Fever of Unknown Origin: A Medical Mystery

fluAll children experience fever at some time or other, usually accompanying a cold or flu. Although fever causes discomfort, irritability and excess drowsiness, it is a condition that is actually beneficial for your child. It is the body’s way of destroying harmful bacteria or viruses that have gained access to the child’s system.

Note that a fever below 101 degrees is considered low grade and is no reason for concern. Only when a fever rises above 101 degrees do we in the medical profession consider it a symptom that may need intervention.

Occasionally, however, both children and adults can develop a fever in which the body temperature is particularly high, long-lasting or reappears at frequent intervals. The fever doesn’t seem to fit with any easily detected illness, such as conditions associated with a cough, ear pain or pain with urination. This condition is called “fever of unknown origin.”

The Search for Causes

Typically, fevers respond to anti-fever medication, such as acetaminophen or ibuprofen, cool compresses, fluids and rest. When those measures prove ineffective, the search is on for underlying conditions that may trigger the body’s fever response.

At 24/7 Pediatric Care Centers, our pediatricians will conduct a thorough physical examination and order a series of tests to rule out possible causes. Blood tests, a urine test and a chest x-ray are the first to be performed. If those do not solve the mystery, further testing may be carried out on an outpatient basis. If a cause still cannot be found, the child may be hospitalized for more advanced laboratory and imaging studies.

The Usual Suspects

Eventually, most testing turns up a cause of the persistent fever. Some of the more common causes are infection, connective tissues disease, parasites, or a neurological problem.

Sometimes, however, the mystery is never solved and the fever of unknown origin goes away on its own.


Be reassured that fevers of unknown origin do not occur frequently. If your child does develop a fever, our pediatricians are highly trained in detecting the causes underlying simple fevers or ones that accompany a more complicated illness.

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24/7 Pediatric Care Centers are Jacksonville pediatricians, Jacksonville Beach pediatricians, and Fleming Island pediatricians providing care for children from newborn to 18 years. Our 24-hour office also provides services for non-life-threatening illnesses to registered patients 24 hours a day.

24/7 Pediatric Care Centers is not a substitute for Emergency or Trauma-related medical care.
If you feel your child is experiencing a life-threatening event, immediately call 911.