What are the transmission cycles of yellow fever. How is yellow fever diagnosed and treated. What are the key preventive measures against yellow fever. Why is yellow fever considered a re-emerging disease. How does yellow fever affect different organ systems.

The Etiology and Transmission of Yellow Fever

Yellow fever is caused by an RNA virus belonging to the Flavivirus genus. This virus is closely related to those responsible for West Nile, St. Louis, and Japanese encephalitis. The primary vectors for yellow fever transmission are tree-hole breeding mosquitoes, particularly Aedes aegypti and Haemagogous species.

The virus exhibits three distinct transmission cycles:

1. Jungle cycle
2. Intermediate cycle
3. Urban cycle

The Jungle Cycle

In the jungle cycle, transmission occurs between non-human primates (monkeys) and mosquitoes. Humans become infected when they enter jungle areas and are bitten by infected mosquitoes. This cycle primarily affects individuals who work or visit jungle regions.

The Intermediate Cycle

The intermediate cycle is observed in African savannah regions. It involves humans living or working in areas bordering jungles. Transmission can occur between monkeys and humans or between humans, with mosquitoes serving as vectors in both cases.

The Urban Cycle

The urban cycle begins when a viremic human, who contracted the virus in either the jungle or intermediate cycle, returns to an urban area. These infected individuals can develop significant viremia, allowing them to infect urban mosquitoes, which in turn can transmit the virus to other humans in urban settings.

It’s important to note that person-to-person or primate-to-human transmission has not been reported without the involvement of a mosquito vector. This underscores the critical role of mosquito control in preventing the spread of yellow fever.

Epidemiology and Global Impact of Yellow Fever

While vaccination has significantly decreased worldwide epidemics of yellow fever, the infection has reemerged in many parts of Africa and South America. This resurgence has raised concerns among health authorities and highlights the need for continued vigilance and preventive measures.

Yellow fever affects people of all ages and races, with no inherent immunity observed in any population group. However, the highest mortality rates are reported in infants and the elderly, likely due to their often compromised immune systems.

In the United States, yellow fever is extremely rare. Most cases diagnosed in the country are among unvaccinated travelers returning from sub-Saharan Africa or South America. This emphasizes the importance of vaccination for individuals planning to visit endemic areas.

Why is yellow fever considered a re-emerging disease?

Yellow fever is classified as a re-emerging disease due to several factors:

• Decreased vaccination rates in some regions
• Urbanization and population movement
• Climate change affecting mosquito habitats
• Deforestation bringing humans closer to sylvatic cycles

These factors have contributed to the resurgence of yellow fever in areas where it was previously controlled, highlighting the need for continued surveillance and preventive measures.

Pathophysiology and Clinical Manifestations of Yellow Fever

The yellow fever virus has an incubation period of 3 to 6 days. Once acquired, it rapidly disseminates throughout the body, affecting multiple organ systems. Understanding the pathophysiology of yellow fever is crucial for effective diagnosis and treatment.

How does yellow fever affect different organ systems?

Yellow fever primarily impacts the following organ systems:

1. Liver: The liver is the most significantly affected organ in yellow fever infection. The virus causes extensive damage to hepatocytes, leading to profound jaundice, which gives the disease its characteristic name.
2. Kidneys: The kidneys undergo pathological alterations similar to those in the liver, potentially resulting in acute renal failure.
3. Gastrointestinal tract: When the upper GI tract is involved, gastric acid mixed with blood can produce what is known as “black vomit,” a classic sign of severe yellow fever.
4. Central nervous system: Yellow fever can cause cerebral edema, hemorrhage, and encephalopathy.

The severity of organ involvement varies among patients, with some experiencing mild, self-limited infections while others develop severe, life-threatening disease.

Clinical Presentation and Diagnosis of Yellow Fever

Diagnosing yellow fever requires a thorough travel history and immunization record. The clinical presentation can vary widely, ranging from mild, non-specific symptoms to severe, life-threatening illness.

What are the typical symptoms of yellow fever?

Patients with yellow fever may present with the following symptoms:

• Headache
• Malaise
• Jaundice
• Fever
• Muscle pain (myalgia)
• Nausea and vomiting
• Abdominal pain
• Bleeding tendencies (in severe cases)

It’s important to note that many of these symptoms are non-specific and can be seen in various other infectious diseases. This non-specificity can lead to delayed diagnosis, especially in non-endemic areas.

How is yellow fever diagnosed?

The diagnosis of yellow fever involves a combination of clinical assessment, laboratory tests, and epidemiological information:

1. Travel history: Recent travel to or residence in an endemic area is a crucial piece of information.
2. Vaccination history: Determining whether the patient has been vaccinated against yellow fever is essential.
3. Clinical symptoms: The presence of characteristic symptoms, especially jaundice and bleeding tendencies, can suggest yellow fever.
4. Laboratory findings: Liver function tests, complete blood count, and coagulation studies can provide supportive evidence.
5. Serological tests: Detection of yellow fever-specific IgM antibodies or viral RNA can confirm the diagnosis.

Early diagnosis is crucial for appropriate patient management and implementation of public health measures to prevent further transmission.

Treatment Approaches for Yellow Fever

Currently, there is no specific antiviral therapy for yellow fever. Treatment primarily focuses on supportive care and management of symptoms and complications.

What are the key components of yellow fever treatment?

The treatment approach for yellow fever includes:

• Fluid and electrolyte management
• Pain relief and fever reduction
• Management of bleeding complications
• Renal replacement therapy if acute kidney injury develops
• Intensive care support for severe cases

In severe cases, patients may require blood transfusions, dialysis, or mechanical ventilation. The mortality rate for severe yellow fever can approach 50%, underscoring the importance of early recognition and aggressive supportive care.

Prevention Strategies and Vaccination

Prevention is the cornerstone of yellow fever control. Vaccination and mosquito bite prevention are the two primary strategies for avoiding yellow fever infection.

How effective is the yellow fever vaccine?

The yellow fever vaccine is highly effective, providing lifelong immunity in most individuals after a single dose. The vaccine is recommended for:

• Travelers to endemic areas
• Laboratory workers handling the virus
• Residents of endemic areas as part of routine immunization programs

The vaccine is generally safe, but there are some contraindications and precautions to consider, such as egg allergy, immunosuppression, and age extremes.

What are other preventive measures against yellow fever?

In addition to vaccination, other preventive measures include:

1. Using insect repellents containing DEET or picaridin
2. Wearing long-sleeved shirts and long pants
3. Using bed nets in endemic areas
4. Avoiding outdoor activities during peak mosquito hours
5. Eliminating mosquito breeding sites in urban areas

These measures not only protect against yellow fever but also other mosquito-borne diseases prevalent in tropical and subtropical regions.

Global Health Initiatives and Future Challenges

Yellow fever remains a significant global health concern, particularly in Africa and South America. International health organizations, including the World Health Organization (WHO), have implemented various initiatives to control and prevent yellow fever outbreaks.

What are the current global strategies for yellow fever control?

The WHO’s Global Strategy to Eliminate Yellow Fever Epidemics (EYE) focuses on three main objectives:

1. Protect at-risk populations through vaccination
2. Prevent international spread
3. Contain outbreaks rapidly

These strategies involve improving surveillance systems, increasing vaccine production and distribution, and enhancing mosquito control efforts in endemic areas.

What challenges lie ahead in yellow fever control?

Despite significant progress, several challenges remain in the global fight against yellow fever:

• Vaccine shortages during large outbreaks
• Urbanization and population movement increasing transmission risks
• Climate change potentially expanding mosquito habitats
• Maintaining high vaccination coverage in endemic areas
• Improving diagnostic capabilities in resource-limited settings

Addressing these challenges will require continued international cooperation, investment in research and development, and strengthening of public health infrastructure in endemic regions.

The Role of Healthcare Professionals in Yellow Fever Management

Healthcare professionals play a crucial role in the prevention, diagnosis, and management of yellow fever. Their responsibilities extend beyond individual patient care to include public health measures and community education.

How can healthcare professionals contribute to yellow fever control?

Healthcare professionals can contribute to yellow fever control through various means:

1. Maintaining a high index of suspicion for yellow fever in travelers from endemic areas
2. Providing pre-travel counseling and vaccination recommendations
3. Promptly reporting suspected cases to public health authorities
4. Educating patients and communities about mosquito bite prevention
5. Participating in surveillance and outbreak response activities

Interprofessional collaboration is essential for effective management of yellow fever cases and prevention of outbreaks. This includes coordination between primary care providers, infectious disease specialists, public health officials, and laboratory personnel.

What are the key areas for ongoing research in yellow fever?

Ongoing research in yellow fever focuses on several key areas:

• Development of antiviral therapies
• Improvement of diagnostic tests, especially rapid point-of-care tests
• Understanding the long-term effects of yellow fever infection
• Enhancing vaccine production and distribution methods
• Investigating the impact of climate change on yellow fever epidemiology

These research efforts aim to improve our ability to prevent, diagnose, and treat yellow fever, ultimately reducing its global health impact.

In conclusion, yellow fever remains a significant public health challenge, particularly in endemic regions of Africa and South America. While vaccination and mosquito control measures have greatly reduced the global burden of the disease, ongoing vigilance and international cooperation are essential to prevent resurgence and control outbreaks. Healthcare professionals play a vital role in this effort, from individual patient care to participation in broader public health initiatives. As we continue to face challenges such as climate change and urbanization, ongoing research and adaptation of control strategies will be crucial in the fight against yellow fever.

Yellow Fever – StatPearls – NCBI Bookshelf

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.

StatPearls [Internet].

Show details

Search term

Leslie V. Simon; Muhammad F. Hashmi; Klaus D. Torp.

Author Information and Affiliations

Last Update: February 19, 2023.

Continuing Education Activity

Yellow fever is a mosquito-borne viral illness found in tropical and subtropical areas in South America and Africa. Transmission is primarily via Aedes and Haemagogus mosquitos. It can present with varying clinical features ranging from a self-limited, mild febrile illness to severe hemorrhage and liver disease. This activity reviews the evaluation and management of yellow fever and highlights the role of the interprofessional team in the recognition and management of this condition.

Objectives:

• Review the pathophysiology of yellow fever.

• Identify the typical presentation of a patient with yellow fever.

• Summarize reasons for a delayed diagnosis of yellow fever.

• Explain the interprofessional team strategies for improving care coordination and communication regarding the management of patients with yellow fever.

Access free multiple choice questions on this topic.

Introduction

Yellow fever is a mosquito-borne viral illness found in tropical and subtropical areas in South America and Africa. Transmission is primarily via Aedes and Haemagogus species of mosquito. It can present with varying clinical features ranging from a self-limited, mild febrile illness to severe hemorrhage and liver disease. The “yellow” comes from jaundice that affects some patients with severe disease. The disease is diagnosed by history travel to an endemic area, exposure to infected mosquitoes, vaccination history, symptoms, and laboratory findings. Most cases are self-limited and resemble many other common viral infections. Of those who develop severe disease mortality can approach 50%. Unlike many other mosquito-transmitted viruses, infected humans are not dead-end hosts and may infect mosquitoes during periods of viremia and spread the virus. There is no specific antiviral therapy, but there is an effective vaccine recommended for travelers to endemic areas. Other than vaccination, prevention of mosquito bites is the best way to avoid contracting the virus.[1][2][3]

Etiology

The virus is an RNA virus of the genus Flavivirus, closely related to the viruses that cause West Nile, St. Louis, and Japanese encephalitis. Tree-hole breeding mosquitoes, such as Aedes aegypti and Haemagogous species, transmit yellow fever during the rainy season. The yellow fever virus has three distinct transmission cycles: jungle, intermediate, and urban. The jungle cycle involves transmission between non-human primates (monkeys) and mosquitoes. Humans are infected through infected mosquito bites while visiting or working in the jungle. The intermediate cycle occurs in the African savannah and involves humans who live or work in jungle border areas. Transmission may be between monkeys and humans or humans via mosquito vectors. The urban cycle involves a viremic human who contracted the virus in either the jungle or intermediate cycle who then returns to an urban area. Humans develop significant viremia to infect mosquitoes, which can then transmit the virus to other humans in urban areas. Person to person or primate to human transmission has not been reported without the involvement of a mosquito vector. [4][5]

Epidemiology

Vaccination has decreased worldwide epidemics of yellow fever, but the infection has reemerged in many parts of Africa and South America. No one is immune from yellow fever, and it occurs in people of all ages and races. The highest mortality rates are reported in infants and the elderly, who often have depressed immune systems. yellow fever is very rare in the United States. Most cases are diagnosed in unvaccinated travelers to sub-Saharan Africa or South America. While most people develop a self-limited infection, those who develop severe disease.[6]

Pathophysiology

The incubation period is 3 to 6 days. Once acquired, the virus quickly spreads to multiple organs in the body. The liver is the most important organ affected by yellow fever. It produces profound jaundice due to liver damage. The kidneys also undergo similar pathological alterations and can lead to acute renal failure. When the upper gastrointestinal (GI) tract is involved, the gastric acid mixed with blood produces what is known as black vomit. Central nervous system (CNS) features include cerebral edema and hemorrhage. Encephalopathy is also a common feature of yellow fever.[7][8]

History and Physical

The diagnosis requires a thorough travel history and record of immunization. Patients may present with headache, malaise, jaundice, and myalgias with severe back pain commonly reported.

The incubation period is 3-7 days, with most individuals having mild flu like illness. About 15% of cases have severe symptoms including chills, low back pain, headache, and fever.

There is a period of remission which may last 24-48 hours. This may be followed by a return of symptoms and marked intoxication. During this stage, the hepatorenal disease is common and carries a high mortality.

A physical exam may reveal the Faget sign or pulse fever dissociation, facial flushing, and conjunctival injection. During the most toxic phase, patients develop jaundice, dark urine, and vomiting. Bleeding may occur from mucous membranes and in the gastrointestinal tract. Symptoms may mimic those of malaria, leptospirosis, viral hepatitis, other hemorrhagic fevers, dengue, and other flavivirus infections.

Evaluation

Rapid detection methods include the detection of yellow fever antigen using monoclonal enzyme immunoassay in serum specimens and detection of viral genome sequences using polymerase chain reaction (PCR) assay. Yellow fever can be diagnosed using ELISA and serology titers of antibodies. Other investigations depend on what organ is involved. If there is evidence of altered mentation, a lumbar puncture and a CT scan are performed. Blood work may reveal leukopenia with elevated transaminase levels. Neutropenia is common during the first week of the infection.

If the liver is involved, the coagulation profile may be abnormal. Elevation in creatinine, hypoglycemia and metabolic acidosis are strongly associated with a very poor prognosis.

Most yellow fever specific testing can be done at the CDC, but reports will be sent to the state health department. When sending blood samples directly to the CDC, the health department should be informed.[3]

A chest x-ray is done in patients with respiratory distress because of the pulmonary edema. ECG may identify prolonged QT and PR intervals. Arrhythmias are common when the myocardium is affected.

Treatment / Management

Yellow fever is a reportable infection. Once the virus is contracted, symptoms develop after 3 to 6 days. There is no specific treatment, but severe cases require aggressive supportive care and hydration. Patients should be managed in the intensive care unit (ICU) and closely monitored for disseminated intravascular coagulation (DIC), hemorrhage, kidney, and liver dysfunction. Coagulopathy is managed with fresh frozen plasma, and renal failure may require dialysis. Even though yellow fever is not transmitted from person to person, isolation of the individual should be undertaken until the diagnosis is confirmed. Universal precautions are required when looking after patients with yellow fever although person-person transmission of the virus is unlikely. Infected patients should avoid mosquitoes, as they may transmit the virus to mosquitoes, which can serve as vectors for infection other patients.

Since there is no effective treatment or vaccine, prevention is critical.  This is best accomplished by avoiding mosquito bites entirely. Even very short periods outdoors can lead to exposure to mosquito bites, so people should wear proper protective clothing. This protection includes long sleeves, long pants, socks, and closed-toe shoes. Pant legs can be tucked into socks to prevent bites to exposed ankles. Transmission is common during the warmer months, and mosquitoes may bite through very thin clothing, so treating clothing with repellents containing permethrin, DEET, oil of lemon eucalyptus, or other EPA-registered insect repellants will reduce this risk. Permethrin should not be applied directly to the skin, but when applied to clothing, it provides protection even after the clothing is washed. Transmission is most frequent when mosquitoes feed, between dawn and dusk, so outdoor activities during this period should be avoided. However, one of the mosquitos responsible for transmitting the virus, Aedes Aegypty, feeds during the daytime; so there is no safe time during the day for a traveler without repellent and wearing protective clothing. Travelers should sleep in air-conditioned spaces or use mosquito nets or screens to prevent bites during sleep. Standing water is a breeding ground for mosquitoes, so flower pots, buckets, and other containers should be drained. Children’s wading pools should be emptied and stored on their sides, and tire swings should have holes drilled into the bottom to allow trapped water to drain.

There is a safe and highly effective live-attenuated vaccine available to prevent yellow fever. A single dose confers lifelong immunity and is effective within 30 days for 99% of patients. Patients with relative contraindications to live attenuated vaccine who plan to travel to endemic areas should review the recommendations for vaccination prior to travel.[9][10][11]

Differential Diagnosis

The differential diagnosis of yellow fever is broad and makes a careful travel history important. It includes:

• Viral hemorrhagic fevers

• Viral hepatitis

• Malaria

• Lassa fever

• Ebola virus

• Typhoid fever

• Dengue fever

• Disseminated Intravascular Coagulation

• Louse-borne relapsing fever

• West Nile virus encephalitis

• Japanese encephalitis

• Herpes simplex encephalitis

• Eastern and Western equine encephalitis

• Venezuelan Equine encephalitis

• Enterovirus meningitis

• Mycoplasma meningitis

• Cytomegalovirus infection in immunocompromised host

• Tuberculous meningitis

• Nipah virus infection

• Rocky Mountain spotted fever

• Fungal meningitis

• Leptospirosis

• Neurocysticercosis

• Amebic meningoencephalitis 

Prognosis

Most cases are subclinical or mildly symptomatic with an excellent prognosis. About 15% of symptomatic patients will develop severe disease. Most will recover, but after a bout of yellow fever, full recovery may take weeks or months. In most cases, there is a reversal of the liver and renal dysfunction. Death occurs in 30% to 50% of patients with severe disease. All travelers to endemic areas should be vaccinated if they are candidates for the live attenuated vaccine.

Death often occurs within 2 weeks during the toxic phase of the infection. Unvaccinated travelers to endemic areas are at high risk for developing symptomatic disease compared to the natives, who have acquired immunity. Rare cases of neurologic and viscerotropic disease have been reported following vaccination.

Complications

• Multiorgan failure

• ARDS

• Sepsis

• Respiratory failure

• Myocarditis

• Encephalitis

• Hemorrhage

• DIC

Pearls and Other Issues

Continuous medical education can be obtained through the CDC website regarding yellow fever and yellow fever vaccine.

Enhancing Healthcare Team Outcomes

Yellow fever is endemic in many parts of the world. The key to this infection is prevention. While the acute infection is managed by an interprofessional group of healthcare professionals, prevention is best done by a coordinated effort of educating patients by the primary care provider, infectious disease nurse, and pharmacist. All travelers to endemic regions should be educated about the vaccine, which confers lifelong immunity. Rarely some individuals may require a booster dose after ten years before traveling to an endemic area. Further, all laboratory workers who regularly handle yellow fever containing blood samples should have their neutralizing antibody titers measured every ten years to determine if they need a booster shot. The pharmacist and nurse should also educate the traveler on wearing long-sleeved garments, sleeping under a net and using DEET containing repellant spray.

Since there is no effective treatment or vaccine, prevention is critical.   This is best accomplished by avoiding mosquito bites entirely. Even very short periods outdoors can lead to exposure to mosquito bites, so people should wear proper protective clothing. This protection includes long sleeves, long pants, socks, and closed-toe shoes. Pant legs can be tucked into socks to prevent bites to exposed ankles. Transmission is common during the warmer months, and mosquitoes may bite through very thin clothing, so treating clothing with repellents containing permethrin, DEET, oil of lemon eucalyptus, or other EPA-registered insect repellants will reduce this risk. Permethrin should not be applied directly to the skin, but when applied to clothing, it provides protection even after the clothing is washed. Transmission is most frequent when mosquitoes feed, between dawn and dusk, so outdoor activities during this period should be avoided. However, one of the mosquitos responsible for transmitting the virus, Aedes Aegypty, feeds during the daytime; so there is no safe time during the day for a traveler without repellent and wearing protective clothing. Travelers should sleep in air-conditioned spaces or use mosquito nets or screens to prevent bites during sleep. Standing water is a breeding ground for mosquitoes, so flower pots, buckets, and other containers should be drained. Children’s wading pools should be emptied and stored on their sides, and tire swings should have holes drilled into the bottom to allow trapped water to drain.

It is very unlikely that yellow fever will be eradicated anytime soon. The mosquitoes also transmit the sylvatic form via nonhuman primates. Additionally, deforestation and urbanization have reintroduced the virus into the cities. Plus, there is a limited amount of resources available. [12][13](Level V)

Outcomes

Yellow fever can be self-limited or in some cases be life-threatening. Data indicate that about 10-25% of patients will develop severe symptoms that include jaundice, fever, renal and liver failure. The case fatality rates are slightly lower in West Africa compared to South America. However, the ultimate mortality depends on the virulence of the infecting strain and patient susceptibility. Overall, about 3-70% of patients die after contracting yellow fever; the higher mortality is usually in patients with liver and renal damage. Deaths tend to occur within the first 10 days of the toxic phase. Both infants and the elderly are more likely to die than other individuals. Individuals who are unvaccinated usually develop more severe disease than natives. Finally, there are rare cases of post-vaccination neurological deficits and viscerotropic disease leading to death.[14][15] (Level V)

Review Questions

• Access free multiple choice questions on this topic.

• Comment on this article.

Figure

Mosquito carried diseases, Zika virus, Dengue fever, West Nile Fever, Chikungunya, Yellow Fever, Malaria. Contributed by National Institutes of Health (NIH)

Figure

Aedes species mosquito. Image courtesy of S Bhimji MD

Figure

Faget sign. Image courtesy Statpearls

References

1.

Chen LH, Kozarsky PE, Visser LG. What’s Old Is New Again: The Re-emergence of Yellow Fever in Brazil and Vaccine Shortages. Clin Infect Dis. 2019 May 02;68(10):1761-1762. [PubMed: 30204852]

2.

Sanna A, Andrieu A, Carvalho L, Mayence C, Tabard P, Hachouf M, Cazaux CM, Enfissi A, Rousset D, Kallel H. Yellow fever cases in French Guiana, evidence of an active circulation in the Guiana Shield, 2017 and 2018. Euro Surveill. 2018 Sep;23(36) [PMC free article: PMC6134805] [PubMed: 30205871]

3.

Leong WY. New diagnostic tools for yellow fever. J Travel Med. 2018 Jan 01;25(1) [PubMed: 30184173]

4.

Javelle E, Gautret P, Raoult D. Towards the risk of yellow fever transmission in Europe. Clin Microbiol Infect. 2019 Jan;25(1):10-12. [PubMed: 30170135]

5.

Kaul RB, Evans MV, Murdock CC, Drake JM. Spatio-temporal spillover risk of yellow fever in Brazil. Parasit Vectors. 2018 Aug 29;11(1):488. [PMC free article: PMC6116573] [PubMed: 30157908]

6.

Chippaux JP, Chippaux A. Yellow fever in Africa and the Americas: a historical and epidemiological perspective. J Venom Anim Toxins Incl Trop Dis. 2018;24:20. [PMC free article: PMC6109282] [PubMed: 30158957]

7.

Barrett ADT. The reemergence of yellow fever. Science. 2018 Aug 31;361(6405):847-848. [PubMed: 30139914]

8.

Faria NR, Kraemer MUG, Hill SC, Goes de Jesus J, Aguiar RS, Iani FCM, Xavier J, Quick J, du Plessis L, Dellicour S, Thézé J, Carvalho RDO, Baele G, Wu CH, Silveira PP, Arruda MB, Pereira MA, Pereira GC, Lourenço J, Obolski U, Abade L, Vasylyeva TI, Giovanetti M, Yi D, Weiss DJ, Wint GRW, Shearer FM, Funk S, Nikolay B, Fonseca V, Adelino TER, Oliveira MAA, Silva MVF, Sacchetto L, Figueiredo PO, Rezende IM, Mello EM, Said RFC, Santos DA, Ferraz ML, Brito MG, Santana LF, Menezes MT, Brindeiro RM, Tanuri A, Dos Santos FCP, Cunha MS, Nogueira JS, Rocco IM, da Costa AC, Komninakis SCV, Azevedo V, Chieppe AO, Araujo ESM, Mendonça MCL, Dos Santos CC, Dos Santos CD, Mares-Guia AM, Nogueira RMR, Sequeira PC, Abreu RG, Garcia MHO, Abreu AL, Okumoto O, Kroon EG, de Albuquerque CFC, Lewandowski K, Pullan ST, Carroll M, de Oliveira T, Sabino EC, Souza RP, Suchard MA, Lemey P, Trindade GS, Drumond BP, Filippis AMB, Loman NJ, Cauchemez S, Alcantara LCJ, Pybus OG. Genomic and epidemiological monitoring of yellow fever virus transmission potential. Science. 2018 Aug 31;361(6405):894-899. [PMC free article: PMC6874500] [PubMed: 30139911]

9.

Lee H, Halverson S, Ezinwa N. Mosquito-Borne Diseases. Prim Care. 2018 Sep;45(3):393-407. [PubMed: 30115330]

10.

Callender DM. Management and control of yellow fever virus: Brazilian outbreak January-April, 2018. Glob Public Health. 2019 Mar;14(3):445-455. [PubMed: 30122143]

11.

Peyraud N, Quéré M, Duc G, Chèvre C, Wanteu T, Reache S, Dumont T, Nesbitt R, Dahl E, Gignoux E, Albela M, Righetti A, Bottineau MC, Cabrol JC, Sarafini M, Nzalapan S, Lechevalier P, Rambaud C, Rull M. A post-conflict vaccination campaign, Central African Republic. Bull World Health Organ. 2018 Aug 01;96(8):540-547. [PMC free article: PMC6083398] [PubMed: 30104794]

12.

Konan YL, Coulibaly ZI, Allali KB, Tétchi SM, Koné AB, Coulibaly D, Ekra KD, Doannio JM, Oudéhouri-Koudou P. [Management of the yellow fever epidemic in 2010 in Séguéla (Côte d’Ivoire): value of multidisciplinary investigation]. Sante Publique. 2014 Nov-Dec;26(6):859-67. [PubMed: 25629680]

13.

Bassolé A. [In Burkina Faso: general mobilization in favor of the “vaccination commando”]. Hygie. 1986 Mar;5(1):31-4. [PubMed: 3699829]

14.

Zahouli JBZ, Koudou BG, Müller P, Malone D, Tano Y, Utzinger J. Urbanization is a main driver for the larval ecology of Aedes mosquitoes in arbovirus-endemic settings in south-eastern Côte d’Ivoire. PLoS Negl Trop Dis. 2017 Jul;11(7):e0005751. [PMC free article: PMC5526600] [PubMed: 28704434]

15.

Barte H, Horvath TH, Rutherford GW. Yellow fever vaccine for patients with HIV infection. Cochrane Database Syst Rev. 2014 Jan 23;(1):CD010929. [PubMed: 24453061]

Disclosure: Leslie Simon declares no relevant financial relationships with ineligible companies.

Disclosure: Muhammad Hashmi declares no relevant financial relationships with ineligible companies.

Disclosure: Klaus Torp declares no relevant financial relationships with ineligible companies.

Copyright © 2023, StatPearls Publishing LLC.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
(
http://creativecommons.org/licenses/by-nc-nd/4.0/
), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

Bookshelf ID: NBK470425PMID: 29262028

Yellow fever

Yellow fever

• All topics »
• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z
• Resources »
  • Fact sheets
  • Facts in pictures
  • Multimedia
  • Publications
  • Questions & answers
  • Tools and toolkits
• Popular »
  • Air pollution
  • Coronavirus disease (COVID-19)
  • Hepatitis
  • Monkeypox
• All countries »
• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z
• Regions »
  • Africa
  • Americas
  • South-East Asia
  • Europe
  • Eastern Mediterranean
  • Western Pacific
• WHO in countries »
  • Statistics
  • Cooperation strategies
  • Ukraine emergency
• All news »
  • News releases
  • Statements
  • Campaigns
  • Commentaries
  • Events
  • Feature stories
  • Speeches
  • Spotlights
  • Newsletters
  • Photo library
  • Media distribution list
• Headlines »
• Focus on »
  • Afghanistan crisis
  • COVID-19 pandemic
  • Northern Ethiopia crisis
  • Syria crisis
  • Ukraine emergency
  • Monkeypox outbreak
  • Greater Horn of Africa crisis
• Latest »
  • Disease Outbreak News
  • Travel advice
  • Situation reports
  • Weekly Epidemiological Record
• WHO in emergencies »
  • Surveillance
  • Research
  • Funding
  • Partners
  • Operations
  • Independent Oversight and Advisory Committee
  • WHO’s Health Emergency Appeal 2023
• Data at WHO »
  • Global Health Estimates
  • Health SDGs
  • Mortality Database
  • Data collections
• Dashboards »
  • COVID-19 Dashboard
  • Triple Billion Dashboard
  • Health Inequality Monitor
• Highlights »
  • Global Health Observatory
  • SCORE
  • Insights and visualizations
  • Data collection tools
• Reports »
  • World Health Statistics 2022
  • COVID excess deaths
  • DDI IN FOCUS: 2022
• About WHO »
  • People
  • Teams
  • Structure
  • Partnerships and collaboration
  • Collaborating centres
  • Networks, committees and advisory groups
  • Transformation
• Our Work »
  • General Programme of Work
  • WHO Academy
  • Activities
  • Initiatives
• Funding »
  • Investment case
  • WHO Foundation
• Accountability »
  • Audit
  • Programme Budget
  • Financial statements
  • Programme Budget Portal
  • Results Report
• Governance »
  • World Health Assembly
  • Executive Board
  • Election of Director-General
  • Governing Bodies website
  • Member States Portal
• Home/
• Newsroom/
• Fact sheets/
• Detail/
• Yellow fever

WHO/E. Soteras Jalil

©
Credits

Key facts

• Yellow fever is an infectious disease transmitted by mosquitoes that bite mostly during the day.
• As of 2023, 34 countries in Africa and 13 countries in Central and South America are either endemic for, or have regions that are endemic for, yellow fever.
• Yellow fever is prevented by a vaccine, which is safe and affordable. A single dose of yellow fever vaccine is sufficient to grant life-long protection.
• A modelling study based on African data sources estimated the burden of yellow fever during 2013 was 84 000–170 000 severe cases and 29 000–60 000 deaths (1).

Overview

Yellow fever is an epidemic-prone mosquito-borne vaccine preventable disease that is transmitted to humans by the bites of infected mosquitoes. Yellow fever is caused by an arbovirus (a virus transmitted by vectors such mosquitoes, ticks or other arthropods) transmitted to humans by the bites of infected Aedes and Haemagogus mosquitoes.

These day-biting mosquitoes breed around houses (domestic), in forests or jungles (sylvatic), or in both habitats (semi-domestic). Yellow fever is a high-impact high-threat disease, with risk of international spread, which represents a potential threat to global health security.

Symptoms

The incubation period for yellow fever is 3 to 6 days. Many people do not experience symptoms. Common symptoms include fever, muscle pain, headache, loss of appetite, nausea or vomiting. In most cases, symptoms disappear after 3 to 4 days.

A small percentage of patients enter a second, more toxic phase within 24 hours of recovering from initial symptoms. High fever returns and several body systems are affected, usually the liver and the kidneys. In this phase, people are likely to develop jaundice (yellowing of the skin and eyes, hence the name yellow fever), dark urine, and abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes, or stomach. Half of the patients who enter the toxic phase die within 7–10 days.

Treatment

There is no specific anti-viral drug for yellow fever. Patients should rest, stay hydrated and seek medical advice. Depending on the clinical manifestations and other circumstances, patients may be sent home, be referred for in-hospital management, or require emergency treatment and urgent referral. Treatment for dehydration, liver and kidney failure, and fever improves outcomes. Associated bacterial infections can be treated with antibiotics.

Diagnosis

Yellow fever is difficult to diagnose, especially during the early stages. A more severe case can be confused with malaria, leptospirosis, viral hepatitis, other haemorrhagic fevers, infection with other flaviviruses (such as dengue), and poisoning.

Polymerase chain reaction (PCR) testing in blood can sometimes detect the virus in early stages of the disease. In later stages, testing to identify antibodies is needed (ELISA and PRNT).

Prevention

1. Vaccination

Vaccination is the most important means of preventing yellow fever. The yellow fever vaccine is safe, affordable and a single dose provides life-long protection against yellow fever disease. A booster dose of yellow fever vaccine is not needed.

The vaccine provides effective immunity within 10 days for 80–100% of people vaccinated, and within 30 days for more than 99% of people vaccinated.

Side-effects from the yellow fever vaccine are rare. People who are usually excluded from vaccination include:

• infants aged less than 9 months;
• pregnant women – except during a yellow fever outbreak when the risk of infection is high;
• people with severe allergies to egg protein; and
• people with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or who have a thymus disorder.

In accordance with the International Health Regulations (IHR), countries have the right to require travellers to provide a certificate of yellow fever vaccination. If there are medical grounds for not getting vaccinated, this must be certified by the appropriate authorities.

• Countries with risk of yellow fever transmission and countries requiring yellow fever vaccination (November 2022) (who.int)
• Vaccination requirements and recommendations for international travellers; and malaria situation per country – 2022 edition (who.int)

2. Vector control

The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites, including by applying larvicides to water storage containers and other places where standing water collects.

Preventive measures, such as wearing clothing to minimize skin exposure and repellents are recommended to avoid mosquito bites. The use of insecticide-treated bed nets is limited by the fact that Aedes mosquitos bite during the daytime.

Both vector surveillance and control are components of the prevention and control of vector-borne diseases, especially for transmission control in epidemic situations. For yellow fever, vector surveillance targeting Aedes aegypti and other Aedes species will help inform where there is a risk of an urban outbreak.

3. Epidemic preparedness and response

Prompt detection of yellow fever and rapid response through emergency vaccination campaigns are essential for controlling outbreaks. However, underreporting is a concern; WHO estimates the true number of cases to be 10 to 250 times what is now being reported.

WHO recommends that every at-risk country has at least one national laboratory where basic yellow fever blood tests can be performed.  A confirmed case of yellow fever in an unvaccinated population is considered an outbreak. A confirmed case in any context must be fully investigated. Investigation teams must assess and respond to the outbreak with both emergency measures and longer-term immunization plans.

WHO response

The Eliminate Yellow Fever Epidemics (EYE) Strategy was developed in response to two urban yellow fever outbreaks – in Luanda (Angola) and Kinshasa (Democratic Republic of the Congo), with international exportation to other countries, including China, showing that yellow fever poses a serious global threat requiring new strategic thinking.

The EYE strategy is comprehensive, multi-component and multi-partner. In addition to recommending vaccination activities, it calls for building resilient urban centres, planning for urban readiness, and strengthening the application of the International Health Regulations (2005).

To find out more about the EYE Strategy, click here: Eliminate yellow fever epidemics (EYE) strategy 2017-2026 (who.int)

It is expected that by the end of 2026, almost 1 billion people will be protected against yellow fever through vaccination.

 

References

1. Garske T. et al. Yellow fever in Africa: Estimating the burden of disease and impact of mass vaccination from outbreak and serological data. PLoS Med. 2014;11(5):e1001638 – https://pubmed.ncbi.nlm.nih.gov/24800812/

Related links

General information

• Q&A: Yellow fever
• International Coordinating Group on Vaccine Provision
• Q&A: Fractional doses of the yellow fever vaccine

Technical information

• WHO’s work on yellow fever
• Situation reports

Yellow fever – causes, symptoms, diagnosis and treatment

Yellow fever is an acute natural focal viral infection characterized by a severe course with a predominance of intoxication, icteric and hemorrhagic syndrome. Yellow fever is one of the most dangerous infections. Yellow fever is spread by vector-borne mosquitoes. The incubation period for yellow fever is about a week. her clinic includes severe intoxication up to disorders of consciousness and cardiac activity, hemorrhagic syndrome, hepatosplenomegaly, icterus of the sclera. Treatment of a patient with yellow fever is carried out exclusively in a hospital in the department for especially dangerous infections.

General information

Yellow fever is an acute natural focal viral infection characterized by a severe course with a predominance of intoxication, icteric and hemorrhagic syndrome. Yellow fever is one of the most dangerous infections.

Characteristics of the causative agent

Yellow fever virus – RNA-containing, belongs to the genus Flavivirus, resistant in the external environment. It tolerates freezing well and drying dies within 10 minutes when heated to 60 ° C, and is also easily inactivated by ultraviolet radiation and disinfectant solutions. Does not tolerate acidic environments. The reservoir and source of infection are animals – monkeys, marsupials, rodents and insectivores. A person can become a source of infection only if there is a carrier.

The disease is spread by a transmissible mechanism, the carriers of the virus are mosquitoes. In the Americas, yellow fever is spread by mosquitoes of the genus Haetagogus, in Africa by Aedes (mainly of the species A. Aegypti). Mosquitoes breed near human dwellings, in barrels of water, artificial stagnant reservoirs, flooded basements, etc. Insects are contagious from 9-12 days after the bite of a sick animal or person at a temperature of 25 ° C and after 4 days at 37 ° C. Transmission of the virus at an ambient temperature of less than 18 ° C is not carried out.

In case of contact with blood containing the pathogen on areas of damaged skin or mucous membranes, a contact route of infection is possible (when processing carcasses of sick animals). People have a high natural susceptibility to infection, after the transfer, long-term immunity is formed. The disease is quarantined (due to the special danger), cases of yellow fever epidemics are subject to international registration.

Outbreaks of the disease can be observed in any areas of the vector distribution area, mainly occur in tropical countries. The spread of fever from the focus of the epidemic is carried out during the movement of patients and the movement of mosquitoes during the transportation of goods. Yellow fever epidemics develop when three necessary conditions are present: carriers of the virus, vectors and favorable weather conditions.

Yellow fever pathogenesis

The virus enters the blood during blood sucking from the digestive system of the vector and during the incubation period reproduces and accumulates in the lymph nodes. In the first days of the disease, the virus spreads through the body with the bloodstream, settling in the tissues of various organs (liver and spleen, kidneys, bone marrow, heart muscle and brain) and affecting their vascular system and causing inflammation. As a result of violation of trophism and direct toxic effect of the virus, necrotic destruction of the parenchyma occurs, an increase in the permeability of the vascular wall contributes to hemorrhage.

Symptoms of yellow fever

The incubation period for yellow fever is one week (sometimes 10 days). The disease proceeds with a change in successive phases: hyperemia, short-term remission, venous stasis and convalescence. The phase of hyperemia begins with a sharp rise in temperature, increasing intoxication (headache, body aches, nausea and vomiting of central origin). With the progression of the intoxication syndrome, disorders of the central nervous activity may occur: delirium, hallucinations, impaired consciousness. The patient’s face, neck and shoulder girdle are puffy, hyperemic, there are numerous injections of the sclera, mucous membranes of the mouth, tongue, conjunctiva are bright red. Patients complain of photophobia and lacrimation.

There are toxic disorders of cardiac activity: tachycardia, followed by bradycardia, hypotension. The amount of daily urine decreases (oliguria), a moderate increase in the size of the spleen and liver is noted. Subsequently, the first signs of a developing hemorrhagic syndrome (hemorrhage, bleeding) appear, the sclera acquire an icteric hue.

The phase of hyperemia lasts about 3-4 days, after which a short-term remission occurs (lasting from several hours to a couple of days). The temperature returns to normal, the general state of health and the objective condition of patients improve. With abortive forms of yellow fever, recovery occurs later, but most often, after a short-term remission, the body temperature rises again. In general, the febrile period is usually 8-10 days from the onset of the disease. In severe cases, after a short-term remission, a phase of venous stasis begins, manifested by severe pallor and cyanosis of the skin, rapidly developing jaundice, petechiae, ecchymatosis, and purpura are common. There is hepatosplenomegaly.

The condition of patients worsens significantly, hemorrhagic symptoms are pronounced, patients note vomiting with blood, melena (tarry feces is a sign of intense intestinal bleeding), bleeding from the nose, internal hemorrhages may be noted. Oliguria usually progresses (up to anuria), bloody impurities are also noted in the urine. In half of the cases, the disease progresses with the development of severe fatal complications. With a favorable course, a long period of convalescence occurs, the clinical symptoms gradually regress. It is possible to preserve a variety of functional disorders with significant tissue destruction. After the transfer of the disease, lifelong immunity is maintained, and there are no repeated episodes.

Severe yellow fever may be complicated by toxic shock, renal and hepatic failure. These complications require intensive care measures, in many cases they lead to death on the 7th-9th day of the disease. In addition, the development of encephalitis is possible.

Diagnosis of yellow fever

In the first days, a general blood test shows leukopenia with a shift of the leukocyte formula to the left, a reduced concentration of neutrophils, platelets. Subsequently, leukocytosis develops. Thrombocytopenia progresses. The hematocrit increases, the content of nitrogen and potassium in the blood increases. A general urine test notes an increase in protein, erythrocytes and cells of a cylindrical epithelium are noted.

Biochemical analysis of blood shows an increase in the amount of bilirubin, the activity of liver enzymes (mainly AST). The isolation of the pathogen is carried out in specialized laboratories, taking into account the particular danger of infection. Diagnosis is made using a bioassay on laboratory animals. Serological diagnostics is carried out by the following methods: RNGA, RSK. ELISA. RNIF and RTNG.

Treatment of yellow fever

Yellow fever is treated as an inpatient in an infectious diseases department specialized in the treatment of highly dangerous infections. Etiotropic therapy for this disease has not yet been developed, treatment is aimed at maintaining immune functions, pathogenetic mechanisms and alleviating symptoms. Patients are shown bed rest, semi-liquid easily digestible food rich in calories, vitamin therapy (vitamins C, P, K). In the first days, it is possible to transfuse the plasma of convalescent donors (the therapeutic effect is negligible).

During the period of fever, patients receive blood transfusions in the amount of 125-150 ml every 2 days, prescribe drugs based on cattle liver extract, iron intramuscularly to compensate for blood loss. In complex therapy, anti-inflammatory (if necessary – corticosteroid), antihistamines, hemostatics, cardiovascular drugs can be prescribed. If necessary, resuscitation measures are taken.

Prognosis and prevention of yellow fever

The prognosis for yellow fever in the case of a mild or abortive course is favorable, with the development of a severe clinic it is aggravated. Complications of infection in half of the cases lead to death.

Prevention of the disease involves the control of the migration of the population and the transport of goods in order to exclude the possibility of importing yellow fever from the epidemic focus. In addition, the destruction of yellow fever vectors in settlements is being carried out. Individual prevention involves the use of protection against insect bites. Specific prophylaxis (vaccination) consists in the administration of a live attenuated vaccine. Immunoprophylaxis is indicated for persons of any age planning a trip to endemic regions 7-10 days before departure.

Yellow fever – causes, symptoms, diagnosis and treatment

Yellow fever is an acute natural focal viral infection characterized by a severe course with a predominance of intoxication, icteric and hemorrhagic syndrome. Yellow fever is one of the most dangerous infections. Yellow fever is spread by vector-borne mosquitoes. The incubation period for yellow fever is about a week. her clinic includes severe intoxication up to disorders of consciousness and cardiac activity, hemorrhagic syndrome, hepatosplenomegaly, icterus of the sclera. Treatment of a patient with yellow fever is carried out exclusively in a hospital in the department for especially dangerous infections.

General information

Yellow fever is an acute natural focal viral infection characterized by a severe course with a predominance of intoxication, icteric and hemorrhagic syndrome. Yellow fever is one of the most dangerous infections.

Characteristics of the causative agent

Yellow fever virus – RNA-containing, belongs to the genus Flavivirus, resistant in the external environment. It tolerates freezing well and drying dies within 10 minutes when heated to 60 ° C, and is also easily inactivated by ultraviolet radiation and disinfectant solutions. Does not tolerate acidic environments. The reservoir and source of infection are animals – monkeys, marsupials, rodents and insectivores. A person can become a source of infection only if there is a carrier.

The disease is spread by a transmissible mechanism, the carriers of the virus are mosquitoes. In the Americas, yellow fever is spread by mosquitoes of the genus Haetagogus, in Africa by Aedes (mainly of the species A. Aegypti). Mosquitoes breed near human dwellings, in barrels of water, artificial stagnant reservoirs, flooded basements, etc. Insects are contagious from 9-12 days after the bite of a sick animal or person at a temperature of 25 ° C and after 4 days at 37 ° C. Transmission of the virus at an ambient temperature of less than 18 ° C is not carried out.

In case of contact with blood containing the pathogen on areas of damaged skin or mucous membranes, a contact route of infection is possible (when processing carcasses of sick animals). People have a high natural susceptibility to infection, after the transfer, long-term immunity is formed. The disease is quarantined (due to the special danger), cases of yellow fever epidemics are subject to international registration.

Outbreaks of the disease can be observed in any areas of the vector distribution area, mainly occur in tropical countries. The spread of fever from the focus of the epidemic is carried out during the movement of patients and the movement of mosquitoes during the transportation of goods. Yellow fever epidemics develop when three necessary conditions are present: carriers of the virus, vectors and favorable weather conditions.

Yellow fever pathogenesis

The virus enters the blood during blood sucking from the digestive system of the vector and during the incubation period reproduces and accumulates in the lymph nodes. In the first days of the disease, the virus spreads through the body with the bloodstream, settling in the tissues of various organs (liver and spleen, kidneys, bone marrow, heart muscle and brain) and affecting their vascular system and causing inflammation. As a result of violation of trophism and direct toxic effect of the virus, necrotic destruction of the parenchyma occurs, an increase in the permeability of the vascular wall contributes to hemorrhage.

Symptoms of yellow fever

The incubation period for yellow fever is one week (sometimes 10 days). The disease proceeds with a change in successive phases: hyperemia, short-term remission, venous stasis and convalescence. The phase of hyperemia begins with a sharp rise in temperature, increasing intoxication (headache, body aches, nausea and vomiting of central origin). With the progression of the intoxication syndrome, disorders of the central nervous activity may occur: delirium, hallucinations, impaired consciousness. The patient’s face, neck and shoulder girdle are puffy, hyperemic, there are numerous injections of the sclera, mucous membranes of the mouth, tongue, conjunctiva are bright red. Patients complain of photophobia and lacrimation.

There are toxic disorders of cardiac activity: tachycardia, followed by bradycardia, hypotension. The amount of daily urine decreases (oliguria), a moderate increase in the size of the spleen and liver is noted. Subsequently, the first signs of a developing hemorrhagic syndrome (hemorrhage, bleeding) appear, the sclera acquire an icteric hue.

The phase of hyperemia lasts about 3-4 days, after which a short-term remission occurs (lasting from several hours to a couple of days). The temperature returns to normal, the general state of health and the objective condition of patients improve. With abortive forms of yellow fever, recovery occurs later, but most often, after a short-term remission, the body temperature rises again. In general, the febrile period is usually 8-10 days from the onset of the disease. In severe cases, after a short-term remission, a phase of venous stasis begins, manifested by severe pallor and cyanosis of the skin, rapidly developing jaundice, petechiae, ecchymatosis, and purpura are common. There is hepatosplenomegaly.

The condition of patients worsens significantly, hemorrhagic symptoms are pronounced, patients note vomiting with blood, melena (tarry feces is a sign of intense intestinal bleeding), bleeding from the nose, internal hemorrhages may be noted. Oliguria usually progresses (up to anuria), bloody impurities are also noted in the urine. In half of the cases, the disease progresses with the development of severe fatal complications. With a favorable course, a long period of convalescence occurs, the clinical symptoms gradually regress. It is possible to preserve a variety of functional disorders with significant tissue destruction. After the transfer of the disease, lifelong immunity is maintained, and there are no repeated episodes.

Severe yellow fever may be complicated by toxic shock, renal and hepatic failure. These complications require intensive care measures, in many cases they lead to death on the 7th-9th day of the disease. In addition, the development of encephalitis is possible.

Diagnosis of yellow fever

In the first days, a general blood test shows leukopenia with a shift of the leukocyte formula to the left, a reduced concentration of neutrophils, platelets. Subsequently, leukocytosis develops. Thrombocytopenia progresses. The hematocrit increases, the content of nitrogen and potassium in the blood increases. A general urine test notes an increase in protein, erythrocytes and cells of a cylindrical epithelium are noted.

Biochemical analysis of blood shows an increase in the amount of bilirubin, the activity of liver enzymes (mainly AST). The isolation of the pathogen is carried out in specialized laboratories, taking into account the particular danger of infection. Diagnosis is made using a bioassay on laboratory animals. Serological diagnostics is carried out by the following methods: RNGA, RSK. ELISA. RNIF and RTNG.

Treatment of yellow fever

Yellow fever is treated as an inpatient in an infectious diseases department specialized in the treatment of highly dangerous infections. Etiotropic therapy for this disease has not yet been developed, treatment is aimed at maintaining immune functions, pathogenetic mechanisms and alleviating symptoms. Patients are shown bed rest, semi-liquid easily digestible food rich in calories, vitamin therapy (vitamins C, P, K). In the first days, it is possible to transfuse the plasma of convalescent donors (the therapeutic effect is negligible).

During the period of fever, patients receive blood transfusions in the amount of 125-150 ml every 2 days, prescribe drugs based on cattle liver extract, iron intramuscularly to compensate for blood loss. In complex therapy, anti-inflammatory (if necessary – corticosteroid), antihistamines, hemostatics, cardiovascular drugs can be prescribed. If necessary, resuscitation measures are taken.

Prognosis and prevention of yellow fever

The prognosis for yellow fever in the case of a mild or abortive course is favorable, with the development of a severe clinic it is aggravated. Complications of infection in half of the cases lead to death.

Prevention of the disease involves the control of the migration of the population and the transport of goods in order to exclude the possibility of importing yellow fever from the epidemic focus. In addition, the destruction of yellow fever vectors in settlements is being carried out.