What are the main causes of long-lasting low-grade fever. How does COVID-19 contribute to persistent fever. What role does pneumonia play in prolonged low-grade fever. How can other infections lead to ongoing low-grade fever. What autoimmune conditions are associated with chronic low-grade fever. How do certain medications impact body temperature regulation. What endocrine disorders can cause persistent low fever. How does cancer potentially manifest as a prolonged low-grade fever.

Understanding Long COVID and Its Impact on Body Temperature

Long COVID, also known as Post-COVID Conditions (PCC), refers to a range of persistent health issues that can occur weeks, months, or even years after an initial COVID-19 infection. One of the common symptoms experienced by individuals with Long COVID is a persistent low-grade fever. This prolonged elevation in body temperature can be concerning and may indicate underlying health issues that require attention.

The Centers for Disease Control and Prevention (CDC) defines Long COVID as signs, symptoms, and conditions that continue or develop after the initial COVID-19 infection. While most people recover from COVID-19 within a few weeks, some individuals experience lingering effects that can significantly impact their daily lives.

Who is at risk for developing Long COVID?

Long COVID can affect anyone who has been infected with SARS-CoV-2, the virus responsible for COVID-19. However, certain factors may increase the likelihood of developing Long COVID:

• Individuals who experienced severe COVID-19 illness
• Unvaccinated individuals
• People with multiple SARS-CoV-2 infections
• Those with pre-existing health conditions

It’s important to note that even people who had mild or asymptomatic COVID-19 cases can develop Long COVID symptoms, including persistent low-grade fever.

The Role of COVID-19 in Persistent Low-Grade Fever

COVID-19 can have lasting effects on various body systems, including the immune system and temperature regulation mechanisms. In some cases, the virus may trigger an ongoing inflammatory response, leading to a persistent low-grade fever.

How does COVID-19 contribute to prolonged fever?

The exact mechanisms behind COVID-19-related persistent fever are not fully understood. However, several theories exist:

1. Viral persistence: Some studies suggest that fragments of the SARS-CoV-2 virus may remain in the body, causing ongoing immune activation.
2. Dysregulated immune response: COVID-19 may lead to an imbalance in the immune system, resulting in chronic inflammation and fever.
3. Autonomic nervous system dysfunction: The virus may affect the body’s temperature regulation centers, leading to prolonged fever.

If you’re experiencing a persistent low-grade fever after recovering from COVID-19, it’s essential to consult with a healthcare provider for proper evaluation and management.

Pneumonia as a Cause of Long-Lasting Low-Grade Fever

Pneumonia, an infection that inflames the air sacs in one or both lungs, can be a significant cause of prolonged low-grade fever. While pneumonia is often associated with acute illness, some cases can lead to lingering symptoms, including persistent fever.

Can pneumonia cause a long-lasting low-grade fever?

Yes, pneumonia can result in a prolonged low-grade fever, especially in cases of:

• Slow-resolving pneumonia
• Atypical pneumonia caused by certain bacteria or viruses
• Complications such as lung abscesses or empyema

In some instances, individuals who have had COVID-19 may develop pneumonia as a complication, further contributing to the persistence of a low-grade fever.

Other Infections Leading to Ongoing Low-Grade Fever

While COVID-19 and pneumonia are significant contributors to persistent low-grade fever, various other infections can also cause this symptom. Some common culprits include:

Which infections can cause prolonged low-grade fever?

• Tuberculosis
• Endocarditis (infection of the heart valves)
• Chronic sinusitis
• Lyme disease
• Chronic viral infections (e.g., Epstein-Barr virus, cytomegalovirus)
• Parasitic infections (e.g., malaria, toxoplasmosis)

These infections can sometimes be challenging to diagnose, especially if other symptoms are mild or non-specific. A thorough medical evaluation, including a detailed history, physical examination, and appropriate diagnostic tests, is crucial for identifying the underlying cause of a persistent low-grade fever.

Autoimmune Conditions and Chronic Low-Grade Fever

Autoimmune disorders occur when the body’s immune system mistakenly attacks healthy cells and tissues. Many autoimmune conditions can manifest with a persistent low-grade fever as one of their symptoms.

Which autoimmune disorders are associated with chronic low-grade fever?

Several autoimmune conditions can present with prolonged low-grade fever, including:

• Rheumatoid arthritis
• Systemic lupus erythematosus (SLE)
• Sjögren’s syndrome
• Adult-onset Still’s disease
• Polymyalgia rheumatica
• Vasculitis

In these conditions, the persistent fever is often accompanied by other symptoms such as joint pain, fatigue, and skin rashes. Diagnosing autoimmune disorders can be complex and may require specialized testing and consultation with a rheumatologist.

The Impact of Medications on Body Temperature Regulation

Certain medications can affect the body’s temperature regulation mechanisms, potentially leading to a persistent low-grade fever. This phenomenon is known as drug-induced fever.

Which medications can cause prolonged low-grade fever?

Some medications associated with drug-induced fever include:

• Antibiotics (e.g., beta-lactams, sulfonamides)
• Anticonvulsants (e.g., phenytoin, carbamazepine)
• Antipsychotics
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Some cardiovascular medications
• Certain cancer treatments

If you suspect that a medication may be causing your persistent low-grade fever, it’s crucial to consult with your healthcare provider before making any changes to your treatment regimen.

Endocrine Disorders and Persistent Low-Grade Fever

The endocrine system plays a vital role in regulating various bodily functions, including temperature control. Certain endocrine disorders can disrupt this delicate balance, potentially leading to persistent low-grade fever.

Which endocrine disorders can cause chronic low-grade fever?

Endocrine conditions that may contribute to prolonged low-grade fever include:

• Hyperthyroidism
• Subacute thyroiditis
• Pheochromocytoma
• Addison’s disease

These disorders often present with other symptoms such as changes in weight, energy levels, and mood. A comprehensive endocrine evaluation, including blood tests and imaging studies, may be necessary to diagnose these conditions accurately.

Cancer and Its Relationship to Prolonged Low-Grade Fever

While not always the case, persistent low-grade fever can sometimes be a sign of underlying cancer. Certain types of cancer are more likely to cause fever as a symptom.

Which types of cancer are associated with chronic low-grade fever?

Cancers that may present with prolonged low-grade fever include:

• Lymphoma
• Leukemia
• Kidney cancer
• Liver cancer
• Colon cancer

It’s important to note that fever alone is not a definitive indicator of cancer. Other symptoms, such as unexplained weight loss, night sweats, and fatigue, may also be present. If you’re experiencing a persistent low-grade fever along with other concerning symptoms, it’s crucial to seek medical attention for proper evaluation.

Understanding the various causes of persistent low-grade fever is essential for proper diagnosis and management. While Long COVID and pneumonia are significant contributors to this symptom, it’s crucial to consider other potential causes such as infections, autoimmune disorders, medications, endocrine issues, and in some cases, cancer. If you’re experiencing a prolonged low-grade fever, consult with your healthcare provider to determine the underlying cause and develop an appropriate treatment plan.

Long COVID or Post-COVID Conditions

Important update: Healthcare facilities

CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination.
Learn more

Long COVID or Post-COVID Conditions

Updated Dec. 16, 2022

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DEFINITION

Long COVID

Some people who have been infected with the virus that causes COVID-19 can experience long-term effects from their infection, known as Long COVID or Post-COVID Conditions (PCC). Long COVID is broadly defined as signs, symptoms, and conditions that continue or develop after initial COVID-19 infection. This definition of Long COVID was developed by the Department of Health and Human Services (HHS) in collaboration with CDC and other partners.

People call Long COVID by many names, including Post-COVID Conditions, long-haul COVID, post-acute COVID-19, long-term effects of COVID, and chronic COVID. The term post-acute sequelae of SARS CoV-2 infection (PASC) is also used to refer to a subset of Long COVID.

What You Need to Know

• Long COVID can include a wide range of ongoing health problems; these conditions can last weeks, months, or years.
• Long COVID occurs more often in people who had severe COVID-19 illness, but anyone who has been infected with the virus that causes COVID-19 can experience it.
• People who are not vaccinated against COVID-19 and become infected may have a higher risk of developing Long COVID compared to people who have been vaccinated.
• People can be reinfected with SARS-CoV-2, the virus that causes COVID-19, multiple times. Each time a person is infected or reinfected with SARS-CoV-2, they have a risk of developing Long COVID.
• While most people with Long COVID have evidence of infection or COVID-19 illness, in some cases, a person with Long COVID may not have tested positive for the virus or known they were infected.
• CDC and partners are working to understand more about who experiences Long COVID and why, including whether groups disproportionately impacted by COVID-19 are at higher risk.

In July 2021, Long COVID was added as a recognized condition that could result in a disability under the Americans with Disabilities Act (ADA). Learn more: Guidance on “Long COVID” as a Disability Under the ADA.

About Long COVID

Long COVID is a wide range of new, returning, or ongoing health problems that people experience after being infected with the virus that causes COVID-19. Most people with COVID-19 get better within a few days to a few weeks after infection, so at least four weeks after infection is the start of when Long COVID could first be identified. Anyone who was infected can experience Long COVID. Most people with Long COVID experienced symptoms days after first learning they had COVID-19, but some people who later experienced Long COVID did not know when they got infected.

There is no test that determines if your symptoms or condition is due to COVID-19. Long COVID is not one illness. Your healthcare provider considers a diagnosis of Long COVID based on your health history, including if you had a diagnosis of COVID-19 either by a positive test or by symptoms or exposure, as well as doing a health examination.

Science at CDC

Scientific evidence and studies behind Long COVID

Science behind Long COVID

How to Get Involved in Long COVID Research

The National Institutes of Health (NIH) is conducting a research project, called the RECOVER Initiative, to understand how people recover from a COVID-19 infection and why some people do not fully recover and develop Long COVID.

RECOVER: Researching COVID to Enhance Recovery

Symptoms

People with Long COVID may experience many symptoms.

People with Long COVID can have a wide range of symptoms that can last weeks, months, or even years after infection. Sometimes the symptoms can even go away and come back again. For some people, Long COVID can last weeks, months, or years after COVID-19 illness and can sometimes result in disability.

Long COVID may not affect everyone the same way. People with Long COVID may experience health problems from different types and combinations of symptoms happening over different lengths of time. Though most patients’ symptoms slowly improve with time, speaking with your healthcare provider about the symptoms you are experiencing after having COVID-19 could help determine if you might have Long COVID.

People who experience Long COVID most commonly report:

General symptoms (Not a Comprehensive List)

• Tiredness or fatigue that interferes with daily life
• Symptoms that get worse after physical or mental effort (also known as “post-exertional malaise”)
• Fever

Respiratory and heart symptoms

• Difficulty breathing or shortness of breath
• Cough
• Chest pain
• Fast-beating or pounding heart (also known as heart palpitations)

Neurological symptoms

• Difficulty thinking or concentrating (sometimes referred to as “brain fog”)
• Headache
• Sleep problems
• Dizziness when you stand up (lightheadedness)
• Pins-and-needles feelings
• Change in smell or taste
• Depression or anxiety

Digestive symptoms

• Diarrhea
• Stomach pain

Other symptoms

• Joint or muscle pain
• Rash
• Changes in menstrual cycles

Symptoms that are hard to explain and manage

Some people with Long COVID have symptoms that are not explained by tests or easy to manage.

People with Long COVID may develop or continue to have symptoms that are hard to explain and manage. Clinical evaluations and results of routine blood tests, chest X-rays, and electrocardiograms may be normal. The symptoms are similar to those reported by people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and other poorly understood chronic illnesses that may occur after other infections. People with these unexplained symptoms may be misunderstood by their healthcare providers, which can result in a long time for them to get a diagnosis and receive appropriate care or treatment.

Review these tips to help prepare for a healthcare provider appointment for Long COVID.

Health conditions

Some people experience new health conditions after COVID-19 illness.

Some people, especially those who had severe COVID-19, experience multiorgan effects or autoimmune conditions with symptoms lasting weeks, months, or even years after COVID-19 illness. Multi-organ effects can involve many body systems, including the heart, lung, kidney, skin, and brain. As a result of these effects, people who have had COVID-19 may be more likely to develop new health conditions such as diabetes, heart conditions, blood clots, or neurological conditions compared with people who have not had COVID-19.

People experiencing any severe illness may develop health problems

People experiencing any severe illness, hospitalization, or treatment may develop problems such as post-intensive care syndrome (PICS).

PICS refers to the health effects that may begin when a person is in an intensive care unit (ICU), and which may persist after a person returns home. These effects can include muscle weakness, problems with thinking and judgment, and symptoms of post-traumatic stress disorder (PTSD), a long-term reaction to a very stressful event. While PICS is not specific to infection with SARS-CoV-2, it may occur and contribute to the person’s experience of Long COVID. For people who experience PICS following a COVID-19 diagnosis, it is difficult to determine whether these health problems are caused by a severe illness, the virus itself, or a combination of both.

People More Likely to Develop Long COVID

Some people may be more at risk for developing Long COVID.

Researchers are working to understand which people or groups of people are more likely to have Long COVID, and why. Studies have shown that some groups of people may be affected more by Long COVID. These are examples and not a comprehensive list of people or groups who might be more at risk than other groups for developing Long COVID:

• People who have experienced more severe COVID-19 illness, especially those who were hospitalized or needed intensive care.
• People who had underlying health conditions prior to COVID-19.
• People who did not get a COVID-19 vaccine.
• People who experience multisystem inflammatory syndrome (MIS) during or after COVID-19 illness.

Health Inequities May Affect Populations at Risk for Long COVID

Some people are at increased risk of getting sick from COVID-19 because of where they live or work, or because they can’t get health care. Health inequities may put some people from racial or ethnic minority groups and some people with disabilities at greater risk for developing Long COVID. Scientists are researching some of those factors that may place these communities at higher risk of getting infected or developing Long COVID.

Preventing Long COVID

The best way to prevent Long COVID is to protect yourself and others from becoming infected. For people who are eligible, CDC recommends staying up to date on COVID-19 vaccination, along with improving ventilation, getting tested for COVID-19 if needed, and seeking treatment for COVID-19 if eligible. Additional preventative measures include avoiding close contact with people who have a confirmed or suspected COVID-19 illness and washing hands or using alcohol-based hand sanitizer.

Research suggests that people who get a COVID-19 infection after vaccination are less likely to report Long COVID, compared to people who are unvaccinated.

CDC, other federal agencies, and non-federal partners are working to identify further measures to lessen a person’s risk of developing Long COVID. Learn more about protecting yourself and others from COVID-19.

Living with Long COVID

Living with Long COVID can be hard, especially when there are no immediate answers or solutions.

People experiencing Long COVID can seek care from a healthcare provider to come up with a personal medical management plan that can help improve their symptoms and quality of life. Review these tips to help prepare for a healthcare provider appointment for Long COVID. In addition, there are many support groups being organized that can help patients and their caregivers.

Although Long COVID appears to be less common in children and adolescents than in adults, long-term effects after COVID-19 do occur in children and adolescents.

Talk to your doctor if you think you or your child has Long COVID. Learn more: Tips for Talking to Your Healthcare Provider about Post-COVID Conditions

Data for Long COVID

Studies are in progress to better understand Long COVID and how many people experience them.

CDC is using multiple approaches to estimate how many people experience Long COVID. Each approach can provide a piece of the puzzle to give us a better picture of who is experiencing Long COVID. For example, some studies look for the presence of Long COVID based on self-reported symptoms, while others collect symptoms and conditions recorded in medical records. Some studies focus only on people who have been hospitalized, while others include people who were not hospitalized. The estimates for how many people experience Long COVID can be quite different depending on who was included in the study, as well as how and when the study collected information. Estimates of the proportion of people who had COVID-19 that go on to experience Long COVID can vary.

CDC posts data on Long COVID and provides analyses, the most recent of which can be found on the U.S. Census Bureau’s Household Pulse Survey.

CDC and other federal agencies, as well as academic institutions and research organizations, are working to learn more about the short- and long-term health effects associated with COVID-19, who gets them and why.

Scientists are also learning more about how new variants could potentially affect Long COVID. We are still learning to what extent certain groups are at higher risk, and if different groups of people tend to experience different types of Long COVID. These studies, including for example CDC’s INSPIRE and NIH’s RECOVER, will help us better understand Long COVID and how healthcare providers can treat or support patients with these longer-term effects. CDC will continue to share information with healthcare providers to help them evaluate and manage these conditions.

CDC is working to:

• Better identify the most frequent symptoms and diagnoses experienced by patients with Long COVID.
• Better understand how many people are affected by Long COVID, and how often people who are infected with COVID-19 develop Long COVID
• Better understand risk factors and protective factors, including which groups might be more at risk, and if different groups experience different symptoms.
• Help understand how Long COVID limit or restrict people’s daily activity.
• Help identify groups that have been more affected by Long COVID, lack access to care and treatment for Long COVID, or experience stigma.
• Better understand the role vaccination plays in preventing Long COVID.
• Collaborate with professional medical groups to develop and offer clinical guidance and other educational materials for healthcare providers, patients, and the public.

Related Pages

• Caring for People with Post-COVID Conditions
• Preparing for Appointments for Post-COVID Conditions
• Researching COVID to Enhance Recovery
• Guidance on “Long COVID” as a Disability Under the ADA

For Healthcare Professionals

• Post-COVID Conditions: Healthcare Providers

Board Certified Family Medicine Physicians

(This is the first in a series of articles that will address things that we often see folks coming in or calling us to see how to handle. This article is going to be on fever. We will also do one on cough, congestion, etc.)

In an adult, a fever can be a common side effect of illnesses like the flu. It represents a temporary rise in body temperature. A fever can be a good sign that your immune system is hard at work fighting an infection or other illness.

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In infants and incredibly young children even a slight fever may be a sign of a more serious illness. In adults a fever is not usually that serious though it can be a warning that things may be getting more serious.

Most of the time, a fever is nothing to worry about and will go away on its own. But if you’re ever unsure, it’s always best to check with your doctor. Here are some general guidelines on when a fever may be cause for concern in an adult:

– A body temperature above 100.4 degrees Fahrenheit is considered a fever.

– A Fever that lasts more than three days or that isn’t responding well to treatment may be cause for concern.

– A Fever accompanied by other symptoms like chest pain, shortness of breath, or severe headache could be serious and should be evaluated by a doctor right away.

– If you have a Fever and are pregnant, elderly, or have a chronic illness like cancer or HIV/AIDS, you should also see a doctor right away.

Fever can be a sign of something serious, but it’s also often just a harmless side effect of an infection or other illness. It can even be caused by certain medicines and your reaction to them. If you’re ever unsure, it’s always best to check with your doctor. With their help, you can figure out what’s causing your fever and how to treat it.

A fever is described as a normally short-term increase in your body temperature that helps your body get rid of illness. It IS part of your immune system. A fever can start when your immune system starts to make more white blood cells to fight an infection. The increase in white blood cells can “message” your brain to heat your body up or initiate a fever.

This causes a fever. and in response, your body will try to cool itself off by altering blood flow to your skin and contracting muscles. This makes you shiver and may cause muscle aches, and pain that anyone who has had the flu can remember…the time they were sick and “ached allover”

Our normal body temperature ranges from 97°F to 99°F (36.1°C to 37.2°C). You are considered to have a fever if your temperature rises above this.

Adults typically have a fever if their body temperature is equal to or above 100.4°F (38°C). This is called a low-grade fever. A high-grade fever happens when your body temperature is 103°F (39.4°C) or above according to most medical texts.

Simple fevers usually go away by themselves after 1 to 3 days. A persistent or recurrent fever may last or keep coming back for up to 14 days. Some diseases (like malaria, etc) can have relapsing fevers for weeks or longer

A fever that lasts longer than normal may be serious even if it is only a slight fever. This is because a recurrent fever might be a sign of a more serious infection or a more serious health condition.

Common fever symptoms in most of us adults include:

• muscle pain

• loss of appetite

• fatigue

• weakness

• sweating

• chills (shivering)

• headaches

Many medical providers suggest that you should call your medical provider sooner than later if you have a high-grade fever — that is if your temperature is 103°F (39.4°C) or higher. Many suggest that you seek medical help if you have any kind of fever for more than three days, or if your symptoms get worse, or change. What are the more serious symptoms to worry about or watch for? A fever may be a sign of serious illness if you have:

• a severe headache

• dizziness

• sensitivity to bright light

• stiff neck or neck pain

• skin rashes

• muscle cramps

• confusion

• seizures

• pain when urinating

• not urinating enough

• difficulty breathing

• frequent vomiting

• dehydration

• stomach pain

• passing dark urine

• passing urine that smells bad

• viral infection (like the flu or a cold)

• bacterial infection (of the skin, the urinary, gi or other body systems)

• fungal infection

• food poisoning

• heat exhaustion

• serious sunburn

• inflammation (from conditions like rheumatoid arthritis)

• a tumor

• blood clots

Some adults that have a chronic health condition or have been treated for a severe illness, may be more likely to get a fever that can be something more serious. Some of those conditions include-

As I mentioned previously some medications and treatments can also suggest a more serious fever, or one more difficult to diagnose, like:

• antibiotics

• blood pressure drugs

• seizure medications

• DTaP vaccine and other vaccines

• pneumococcal vaccine

• steroids

• chemotherapy such as methotrexate, Cytoxan, and azathioprine

• radiation treatment

• post-transplant medications (after kidney, liver, heart etc)

A fever is not normally harmful on its own. Most fevers go away within a few hours to days. Many look upon the fever as evidence that the body is fighting to protect itself from infection and other things. You can always help yourself feel better with these at-home fever remedies (useful with viral infections like flu, or with bacterial infections, like UTI’s or strep throat etc..)

stay hydrated by drinking plenty of fluids, like juices, water, broths etc. .

• soups

• try to eat “lighter foods” that are easier on an upset stomach

• get plenty of rest

• You can use a cool compress, like a damp towel to help cool the body

• take a warm or room temperature sponge bath

• dress in lighter, more comfortable clothing

• keep your thermostat lower

Over-the-counter medications can help ease your fever and symptoms, like headaches and muscle pain:

• ibuprofen (Advil, Motrin)

• acetaminophen (Tylenol)

• naproxen (Aleve, Naprosyn)

Are there other natural or homeopathic treatments for fever?

You can also try these:

teas- chamomile, ginger, lavender

herbs and supplements- echinacea, garlic, goldenseal, ginseng

more fluids- water with honey and lemon, fruit juices like cranberry or blueberry juice etc..

soups- chicken soup, vegetable soup

yogurt- plain yogurt with honey (for adults only)

honey- one tablespoon 3 times a day ( for children one year and older)

warm compress on the forehead or neck area for 20 minutes at a time every few hours as needed.

What is the bottom line?

A fever is not usually harmful, but it might be a sign of something more serious.

Some patients may need treatments for more serious causes of a fever. The treatment depends on the causes. You may need medications to treat serious infections, etc: Things like antivirals, antibiotics (and probiotics) or antifungals.

A fever can be a sign of serious illness. A high fever can also cause serious side effects if it persists for a longer time. So, when is it an emergency, or when should I see my medical provider?

Somethings that suggest that you are having Emergency Symptoms

• seizure or convulsions

• fainting or loss of consciousness

• difficulty breathing

• hives or a rash

• swelling in any part of the body

• confusion

• hallucinations

• severe headache pain

• stiff or painful neck

In closing, let me summarize-

A fever in most healthy adults is usually not harmful on its own. But it can be a sign that your body is dealing with an infection or other illness. In some cases, a high or long-lasting fever can be a sign of a serious illness that could mean that you may need urgent medical care.

Do not ignore a fever. Get plenty of rest and fluids to help your body heal and rid itself of the cause of the fever and the fever too… It is a good rule of thumb to see your medical care provider if you have a fever that lasts longer than 3 days or if you have other severe symptoms.

Most experts agree that if you have a serious chronic condition or have been treated for a serious illness, or if you have recently undergone surgery or other medical procedure, you should let your medical provider know if you have any kind of fever.

Thanks for reading this and sharing. We also welcome your feedback. Dr. P

Author

Robert W. Patterson MD ND
Founder of Back to Basics Medical Practice who has practiced family medicine for 40 years and dedicated his professional life to serving his patients ( and not the insurance companies)

What tests to pass with a long subfebrile temperature in the Optimum medical laboratory in Sochi (Adler)

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1. Home
2. medical reference book
3. Subfebrile temperature

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Subfebrile temperature is the thermal state of the human body at the level of 37-37. 5°C for a long time. In this case, the symptoms of any disease may be completely absent and malaise may appear. We are talking about subfebrile temperature in this condition for many days in a row.

Causes of subfebrile temperature

The thermoregulation system of the human body is controlled by an important part of the brain – the hypothalamus. The influence of endogenous or exogenous substances (pyrogens) provokes a dynamic restructuring of the level of heat transfer.

Factors causing subfebrile temperature are numerous:

• infectious processes – SARS, mononucleosis, influenza, tuberculosis, enterocolitis, herpes – and cytomegaloviruses, AIDS, etc.;
• parasitic infestations – ascariasis, giardiasis, toxoplasmosis, salmonellosis;
• autoimmune pathologies – systemic lupus erythematosus, vasculitis, rheumatoid arthritis, celiac disease;
• inflammatory diseases – cystitis, pancreatitis, pneumonia, pyelonephritis, tonsillitis, otitis;
• disorders of the functional activity of the thyroid gland;
• severe allergic reaction;
• pathological hemolysis causing tissue necrosis in case of heart attack, stroke, traumatic toxicosis.

What tests to take?

Subfebrile temperature is a sign of a number of pathological processes that can occur without severe clinical symptoms. With the problem of prolonged subfebrile condition, you can contact your family doctor, phthisiatrician, otolaryngologist, infectious disease specialist, endocrinologist. However, in order to make a competent diagnosis, a comprehensive examination and a number of laboratory tests will be required:

• General clinical blood and urine tests.
• Rheumatological profile, which allows to detect pathological processes in the articular and connective tissues.
• Fecal analysis.
• General clinical examination of sputum – to detect mycobacterium that causes tuberculosis.
• Blood cultures for sterility – to confirm or refute the presence of pathogenic bacteria.
• Blood tests for HIV and TORCH infections, syphilis, viral hepatitis.
• Bacteriological culture from the nasopharynx.
• Blood test for tumor markers – to detect specific substances that are waste products of a tumor-like formation.
• Blood test for thyroid hormones.

In order to bring the mechanisms of thermoregulation back to normal, it is necessary to treat infectious and inflammatory diseases in a timely manner, avoid psycho-emotional and physical overstrain, quit smoking and alcohol, observe a sleep and rest regimen, and eat rationally. However, it is important to remember that with the frequent occurrence of changes in thermoregulation, it is necessary to seek medical help without delay!

Subfebrile temperature – causes, diagnosis and treatment

Causes of subfebrile temperature

Physiological factors

The rise in temperature to subfebrile during the day is observed during intensive sports training, hard physical work. In such cases, the key causes of temperature fluctuations are increased contractions of muscle fibers and increased heat production. Usually, the indicators return to normal after 1-2 hours. If this does not happen, and the general condition worsens, you should consult a doctor. Subfebrile condition is possible after prolonged exposure to the sun, especially in young children, whose thermoregulatory mechanisms are imperfect.

Emotional reactions

Any changes in the cerebral cortex due to psycho-emotional reactions lead to short-term disturbances in the work of the hypothalamic center of thermoregulation. Such an emotional state is accompanied by subfebrile body temperature, which is more typical for women prone to hysterical reactions. Subfebrile condition can persist for a long time with chronic stress, neuroses and neurosis-like conditions. A person does not tolerate a rise in temperature, he is worried about constant weakness and weakness, apathy, and appetite decreases.

Allergic reactions

In acute allergic reactions, subfebrile condition develops abruptly, in the first hours after contact with the trigger substance. Subfebrile temperature is accompanied by pathognomonic allergic symptoms: redness of the eyes and watery eyes, sneezing, clear discharge from the nose. Disorders persist for the entire period of action of the cause of the allergy. The temperature rarely exceeds 37.5°C. Against the background of a temperature reaction, a widespread rash in the form of blisters often occurs, combined with unbearable itching, swelling and redness of the skin.

SARS

With all respiratory diseases, except for influenza, the temperature rises to subfebrile. Pathogens are mainly localized in the epithelium of the respiratory tract, penetrate into the systemic circulation in small quantities and are not able to have a strong pyrogenic effect. An increase in the thermometer with ARVI is accompanied by an ache all over the body, headache, severe chills. The rise in temperature often occurs gradually, the fever lasts for 3-5 days. Typical causes of subfebrile condition are adenovirus and rhinovirus infection, colds.

ENT pathology

Infection of the upper respiratory tract and ear caused by viruses, or limited bacterial inflammation, causes an increase in temperature to subfebrile numbers. Fever begins after a short (1-2 days) prodromal period, when there is heaviness in the head, pain in the muscles and joints, and drowsiness. Temperature indicators do not exceed 38 ° C, the skin is often pale, a glint in the eyes is characteristic. If left untreated, elevated subfebrile temperature can persist for 2-3 weeks, which is typical for subacute inflammations. Common causes of low fever:

• Ear affection : eustachitis, labyrinthitis, otitis externa and otitis media.
• Sore throat : catarrhal angina, pharyngitis or laryngitis, acute and chronic tonsillitis.
• Diseases of the nose and paranasal sinuses : exacerbation of chronic rhinitis, vasomotor rhinitis, sinusitis.

Diseases of the lower respiratory tract

In simple bronchitis, the body temperature does not rise above 38 degrees, the fever lasts an average of 7-14 days. The general condition remains satisfactory, slight malaise, weakness are disturbing. Specific symptoms include cough, mild sore throat and chest pain. The presence of subfebrile temperature is characteristic of interstitial pneumonia. With this pathology, the temperature reaction comes to the fore and general signs – weakness, shortness of breath, and specific manifestations of pneumonia are slightly expressed.

Viral infections

Most infectious diseases caused by viruses are accompanied by subfebrile temperature, which rises to febrile only in case of severe course with massive viremia. The symptom occurs with a viral infection of any localization: with the involvement of the respiratory, digestive, urinary and other systems. The duration of low-grade fever ranges from several days with intestinal infections to several months in patients with chronic processes. Common viral causes in which subfebrile temperature is observed:

• Gastrointestinal disorders : acute hepatitis (A, B, E), chronic hepatitis B and C, rotavirus enteritis.
• Exanthematous infections : measles and rubella, varicella, roseola infantum.
• Neurological infections : poliomyelitis, lymphocytic choriomeningitis, Japanese encephalitis.
• TORCH – infections : cytomegalovirus, herpes simplex, coxsackieviruses.

HIV infection

1-2 months after infection with the immunodeficiency virus, a constant subfebrile temperature occurs with flu-like symptoms – headaches and muscle pain, weakness. More often, temperature indicators for HIV are in the range of 37.2-37.5 ° C, not changing during the day. Fever is accompanied by fatigue, weakness, loss of appetite, decreased ability to work. Subfebrile body temperature is usually accompanied by skin lesions, characterized by polymorphic rashes.

Chronic bacterial infections

Prolonged subfebrile temperature is characteristic of slow infectious processes. Most often, such a reaction is noted in tuberculosis: the thermometer values ​​​​do not exceed 37. 5 degrees, while the person constantly feels weakness and decreased performance. Sweating at night is characteristic. Periodic low-grade fever throughout the year and even several years is observed with brucellosis, a relapsing variant of Lyme disease. The symptom is combined with pain in the joints, various skin lesions.

Helminthiases

Giardiasis, opisthorchiasis, amoebiasis are causes that stimulate the production of endogenous biologically active substances and pyrogens. With such parasitic invasions, the temperature rises to subfebrile, which is accompanied by dyspeptic disorders. With ascariasis, subfebrile condition occurs during the period of migration of larvae, which is manifested by cough and shortness of breath, polymorphic rashes throughout the body. With helminthiases, subfebrile temperature is often determined against the background of pain and swelling of the joints, urticarial rash.

Fluctuations in female sex hormones

Typical causes of subfebrile temperature in women are a decrease in estrogen levels and hormonal changes during menopause. Subfebrile condition is detected during hot flashes, when it seems that the face and neck are “burning”, bright red spots form on the skin. Patients feel severe headaches, flies flickering before their eyes. Fever sometimes occurs during the first trimester of pregnancy due to increased synthesis of sex hormones. This condition requires a doctor’s consultation in order to exclude the pathological causes of the development of subfebrile temperature.

Intestinal pathology

In inflammatory bowel diseases (ulcerative colitis, Crohn’s disease), the synthesis of active mediators and cytokines, which affect the thermoregulatory center in the hypothalamus, increases. Subfebrile temperature persists for a long time: typically alternating periods of remission with normalization of temperature indicators and periods of exacerbation. The main complaints are abdominal pain, stool disorders, loss of appetite. An alarming sign is the release of blood from the anus during an exacerbation, which indicates a deep destruction of the intestinal mucosa.

Endocrine disorders

Subfebrile temperature often develops with increased synthesis of thyroid hormones, which increase basal metabolism and thermogenesis. The symptom is determined constantly for several months, while the skin becomes hot and moist. Unlike other conditions that occur with a rise in temperature, thyrotoxicosis as a cause of subfebrile condition is characterized by an increase in appetite, resentment, irritability, aggressiveness. Occasionally, a temperature reaction manifests adrenal insufficiency (Addison’s disease).

Autoimmune processes

In systemic connective tissue diseases, subfebrile temperature is more often detected during an exacerbation caused by medication or external influences, less often a symptom is recorded constantly. The main causes of subfebrile condition are lupus erythematosus, rheumatism, vasculitis. Subfebrile temperature in adolescents is often associated with juvenile rheumatoid arthritis. With this collagenosis, the patient is concerned about pain in the joints, morning stiffness of movements, swelling and hyperemia of the skin.

Tumors

Chronic subfebrile temperature, accompanied by weakness, loss of appetite, weight loss, is a typical symptom of the oncological process. The fever starts for no apparent reason and lasts for several months. The appearance changes – the skin becomes pale, dark circles appear under the eyes, patients lose weight by 7-10 kg. The combination of subfebrile temperature, which often occurs in the evenings, with profuse night sweats, swollen lymph nodes is characteristic of leukemia and Hodgkin’s lymphoma.

Iatrogenic effects

Sometimes low-grade fever is the result of medical interventions. In the early postoperative period, fever is a variant of the norm and lasts 2-3 days, after which the indicators should return to normal. An increase in temperature values ​​after a blood transfusion or transplantation of internal organs is an unfavorable sign that indicates the incompatibility of the donor and recipient cells, when the immune system begins to reject the foreign tissue. In this situation, emergency medical attention is required.

Complications of pharmacotherapy

Frequent causes of subfebrile temperature are the use of antibacterial drugs that destroy beneficial microflora, against which opportunistic pathogens begin to dominate. Symptoms are determined 5-7 days after the start of treatment. The use of psychotropic drugs – psychostimulants, antidepressants, which affect all brain structures, causes persistent subfebrile condition up to 37.4-37.6 ° C. The temperature sometimes rises after taking atropine, corticosteroids, antihistamines.

Rare causes

• Postviral asthenia (temperature tail of various infections).
• Foci of chronic infection : inflammation of the appendages, carious teeth, encapsulated abscesses.
• Anemias : iron deficiency, hemolytic, aplastic.
• Pathologies of the urinary system : urethritis, cystitis, chronic pyelonephritis.
• Vegetative-vascular dystonia, thermoneurosis .
• Chronic sepsis .

Diagnostics

Subfebrile temperature is recorded in many diseases, so the primary diagnosis is often done by a general practitioner. Its task is to assess all body systems, identify violations that could lead to a temperature rise. The examination includes advanced laboratory tests of blood and other biological materials, modern instrumental methods. The following have the greatest diagnostic value:

• Blood tests . When evaluating the general analysis, attention is paid to the level of leukocytes and the ratio of different leukocyte fractions, the amount of hemoglobin and erythrocytes. In a biochemical blood test, signs of inflammation are found (C-reactive protein, sialic acids). Liver tests can determine whether low-grade fever may be associated with viral or other liver damage.
• Bacteriological methods . To determine the cause of prolonged subfebrile temperature, a three-time blood sampling and its inoculation on selective nutrient media are performed. For symptoms of a respiratory infection, a throat swab, samples of sputum and mucus from the nose are examined. To identify tuberculosis, it is necessary to collect morning and evening sputum for inoculation on Ziehl-Neelsen medium.
• Serological tests . To clarify the connection between subfebrile temperature and viral infections, precise methods of ELISA, RIF, and PCR are used. These analyzes are widely used to detect markers of viral hepatitis, antibodies to pathogens of intestinal and respiratory diseases. To exclude HIV, immunoblotting and high-quality PCR are performed.
• Sonography . Ultrasound examination serves as a screening method for assessing the condition of the abdominal organs, endocrine glands, and joints. Women are recommended ultrasound of the mammary glands, tumors of which are often the cause of subfebrile temperature. Be sure to perform an ultrasound of the liver to exclude destructive and inflammatory processes.
• Radiological Imaging . Subfebrile temperature occurs with intestinal pathology, therefore barium suspension or full X-ray examination of the digestive tract with contrast is informative. To confirm sinusitis, radiographs of the paranasal sinuses are performed. All patients with subfebrile condition are prescribed X-ray of the lungs.
• Invasive examinations . With dermatomyositis and scleroderma, a biopsy of the affected area of ​​soft tissues is sometimes required for histological examination. If subfebrile temperature is combined with symptoms of intoxication and lymphadenopathy, a biopsy of the lymph node is performed, followed by a cytological examination. Intestinal biopsy is indicated for the differential diagnosis of IBD.
• Refinement methods . In women, the hormonal profile is examined to exclude pathological menopause, pregnancy. Subfebrile temperature in diseases of the respiratory tract requires spirography to assess the function of external respiration. Patients with exudative diathesis are examined by an expanded immunogram and allergological tests.

Treatment

Help before diagnosis

Subfebrile body temperature persisting for several days is a condition that requires immediate referral to a specialist to verify the cause. It is forbidden to take antipyretics, as they interfere with the body’s fight against infection and lubricate the clinical picture. With symptoms of intoxication, a plentiful warm drink (water, juices, herbal teas) is necessary, food should be easily digestible and fortified. It is necessary to limit physical activity, with general malaise, it is advisable to observe bed rest.

Conservative therapy

It is generally accepted among physicians that at subfebrile temperature it is necessary to influence the causes of the condition, and the use of antipyretic drugs is considered inappropriate. Antipyretics are prescribed in exceptional cases for young children who are difficult to tolerate fever and are at risk of developing a convulsive syndrome. After finding out the cause of prolonged subfebrile condition, the following groups of drugs are prescribed:

• Antibiotics . When subfebrile temperature is caused by sluggish infections, long courses of antibacterial agents are needed, selected taking into account the type of pathogenic microflora. In tuberculosis, 3-4 specific drugs are combined for 8-12 months.
• Antivirals . Etiotropic drugs are suitable for the treatment of viral hepatitis, accompanied by subfebrile temperature, HIV infection. Medicines inhibit the reproduction of the pathogen and reduce the viral load in the blood. For respiratory and intestinal infections are not used.
• Non-steroidal anti-inflammatory drugs . In rheumatic diseases, medications are effective that reduce the synthesis of cytokines, relieve pain and stiffness of movements. In the case of long-term therapy, selective COX-2 inhibitors are chosen to reduce side effects from the gastrointestinal tract.
• Vitamins . To strengthen the body and speed up recovery, ascorbic acid, B vitamins are prescribed. Natural antioxidants are useful – tocopherol, retinol. With general exhaustion, metabolic drugs are taken that provide the body with energy.
• Hormones . Estrogen preparations are recommended for women in menopausal age. They eliminate the negative manifestations of hot flashes, subfebrile temperature disappears after a course of hormones. Combined contraceptives have a good therapeutic effect in severe premenstrual syndrome.
• Cytostatics . Antimetabolites are indicated as part of combination chemotherapy for oncopathology. In most cases, they are used simultaneously with radiation therapy. Cytostatics are taken in severe autoimmune processes refractory to treatment with corticosteroids.
• Infusion solutions .