infections
Fever in Adults
Evaluation of Fever in Adults
Usually, a doctor can determine that an infection is present based on a brief history, a physical examination, and occasionally a few simple tests, such as a chest x-ray and urine tests. However, sometimes the cause of fever is not readily identified. When doctors initially evaluate people with an acute fever, they focus on two general issues: Identifying other symptoms such as headache or cough: These symptoms help narrow the range of possible causes. Determining whether the person is seriously or chronically ill: Many of the possible acute viral infections go away on their own and also are difficult for doctors to diagnose specifically (that is, to determine exactly which virus is causing the infection). Limiting testing to people who are seriously or chronically ill can help avoid many expensive, unnecessary, and often fruitless searches. In people with an acute fever, certain signs and characteristics are cause for concern. They include A change in mental function, such as confusion A headache, stiff neck, or both Flat, small, purplish red spots on the skin (petechiae), which indicate bleeding under the skin Low blood pressure Rapid heart rate or rapid breathing Shortness of breath (dyspnea) A temperature that is higher than 104° F (40° C) or lower than 95° F (35° C) Recent travel to an area where a serious infectious disease such as malaria is common (endemic) Recent use of drugs that suppress the immune system (immunosuppressants) People who have any warning signs should see a doctor right away. Such people typically need immediate testing and often admission to a hospital. People without warning signs should call the doctor if the fever lasts more than 24 to 48 hours. Depending on the person's age, other symptoms, and known medical conditions, the doctor may ask the person to come for evaluation or recommend treatment at home. Typically, people should see a doctor if a fever lasts more than 3 or 4 days regardless of other symptoms. Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the fever and the tests that may need to be done. A doctor begins by asking a person about present and previous symptoms and disorders, drugs currently being taken, any blood transfusions, exposure to infections, recent travel, vaccinations, and recent hospitalizations, surgeries, or other medical procedures. The pattern of the fever rarely helps the doctor make a diagnosis. However, a fever that returns every other day or every third day is typical of malaria. Doctors consider malaria as a possible cause only if people have traveled to an area where malaria is common. Recent travel may give the doctor clues to the cause of a fever because some infections occur only in certain areas. For example, coccidioidomycosis (a fungal infection) occurs almost exclusively in the southwestern United States. Recent exposures are also important. For example, people who work in a meatpacking plant are more likely to develop brucellosis (a bacterial infection spread through contact with domestic animals). Other examples include unsafe water or food (such as unpasteurized milk and milk products, and raw or undercooked meat, fish, and shellfish), insect (such as mosquitoes) and tick bites, unprotected sex, and occupational or recreational exposures (such as hunting, hiking, and water sports). Pain is an important clue to the possible source of fever, so the doctor asks about any pain in the ears, head, neck, teeth, throat, chest, abdomen, flank, rectum, muscles, and joints. Other symptoms that help determine the cause of the fever include nasal congestion and/or discharge, cough, diarrhea, and urinary symptoms (frequency, urgency, and pain while urinating). Knowing whether the person has enlarged lymph nodes or a rash (including what it looks like, where it is, and when it appeared in relation to other symptoms) may help the doctor pinpoint a cause. People with recurring fevers, night sweats, and weight loss may have a chronic infection such as tuberculosis or endocarditis (infection of the heart's lining and usually the heart valves). The doctor may also ask about the following: Contact with anyone who has an infection Any known conditions that predispose to infection, such as HIV infection, diabetes, cancer, organ transplantation, sickle cell disease, pacemaker, or heart valve disorders, particularly if an artificial valve is present Any known disorders that predispose to fever without infection, such as lupus, gout, sarcoidosis, an overactive thyroid gland (hyperthyroidism), or cancer Use of any drugs that predispose to infection, such as cancer chemotherapy drugs, corticosteroids, or other drugs that suppress the immune system Use of illicit drugs that are injected The physical examination begins with confirmation of fever. Fever is most accurately determined by measuring rectal temperature, but oral or ear temperature is often measured. Forehead temperature is not as accurate as rectal, but because of the COVID-19 pandemic, doctors may measure forehead temperature to screen people for fever. Armpit temperature is the least accurate, so doctors rarely use it to confirm a fever. Doctors then do a thorough examination from head to toe to check for a source of infection or evidence of disease. The need for testing depends on what the doctor finds during the medical history and physical examination. Otherwise healthy people who have an acute fever and only vague, general symptoms (for example, they feel generally ill or achy) probably have a viral illness that will go away without treatment. Therefore, they do not usually require testing. Exceptions are people in an area where COVID-19 is being spread, people who have been exposed to an animal or insect that carries and transmits a specific disease (called a vector), such as people with a tick bite, and people who have recently been in an area where a particular disorder (such as malaria) is common. If otherwise healthy people have findings that suggest a particular disorder, testing may be needed. Doctors select tests based on those findings. For example, if people have a headache and stiff neck, a spinal tap (lumbar puncture) is done to look for meningitis. If people have a cough and lung congestion, a chest x-ray is done to look for pneumonia. For certain respiratory diseases, such as COVID-19 or influenza, there are rapid molecular tests that can give results within minutes or a few hours. Some rapid tests can be done at home or in a doctor's office on a sample obtained with a cotton swab. Other rapid tests to identify a specific cause of an infection require a blood sample sent to a laboratory. People who are at increased risk of infection, people who appear seriously ill, and older people often need testing even when findings do not suggest a particular disorder. For such people, doctors may do the following: A complete blood count (including the number and proportion of different types of white blood cells) Urine and blood cultures A chest x-ray Urinalysis An increase in the white blood cell count usually indicates infection. The proportion of different types of white blood cells (differential count) gives further clues. For example, an increase in neutrophils suggests a relatively new bacterial infection. An increase in eosinophils suggests the presence of parasites, such as tapeworms or roundworms. Also, blood, urine, and other body fluids may be sent to the laboratory to try to grow the microorganism in a culture. Other blood tests can be used to detect antibodies against specific microorganisms. A fever of unknown origin may be diagnosed when People have a fever of at least 101° F (38.3° C) for several weeks. Extensive investigation does not detect a cause. In such cases, the cause may be an unusual chronic infection (such as Tuberculosis (TB) , Doctors usually do blood tests, including a complete blood count, blood cultures, Liver Blood Tests , and tests to check for connective tissue disorders. Other tests, such as chest x-ray, urinalysis, and urine culture, may be done. Ultrasonography , If these test results are negative, doctors may need to take a sample of tissue from the liver, bone marrow, or another site of suspected infection for biopsy. The sample is then examined under a microscope, cultured, and analyzed. The treatment of FUO is focused on treating the disorder causing the fever if it is known. Doctors may give drugs to lower the body temperature ( Treatment ). 