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Prolonged Fever - Fever of Unknown Origin

Question of the Week


Updated June 02, 2014

Father taking child's temperature
Tom Grill/Photographer's Choice RF/Getty Images
Q. My 7 year old son has had a fever for nearly 10 days now. The fever goes up to about 103.3 and down to normal - a couple of times it has been normal for nearly 24 hours before it spikes again. At first my son was acting very healthy and normal, but the last couple of days he has been feeling very tired and worn out, and is coughing a lot. He was tested for strep a week ago and this came back positive, so he was put on antibiotics. However, the fever did not go and although he now tests negative for strep, he is still sick. A blood count taken one day ago shows a "very healthy blood count" according to his pediatrician. Our son had the flu vaccine about one month ago.

At what point do we need to start getting worried and asking for more tests? It seems to me that 10 days is a very long time to have a fever, and our doctor is not being overly proactive about this. White Plains, NY

A. Having a child with a prolonged fever like this can be frustrating, both for a parent and their Pediatrician.

On the one hand you don't want to overreact and put a child through a lot of unnecessary tests for what could be 'just a virus,' but then you also don't want to miss anything treatable or even more importantly, miss something very serious.

So doctors usually use a step-wise approach when managing a patient like this.

If seen early in the illness, like within the first 3-5 days, they may just decide to observe a child after a full physical exam and considering the child's symptoms. After that, your Pediatrician will likely do more testing if the fever persists, like the strep test and blood count.

At this point, since your child still has a fever, he likely needs to be seen again. This is especially important since you think he is getting worse. If your aren't comfortable seeing your Pediatrician again, then consider getting a second opinion from another Pediatrician or by going to the ER at a Children's Hospital.

Further testing might include a chest xray, urinalysis, blood culture, testing for mono, a repeat blood count, liver function tests, a PPD to test for tuberculosis, and a sedimentation rate (ESR) and C-reactive protein (CRP) test.

When evaluating a child with a fever of unknown origin (FUO), after several weeks, testing for less common things is also eventually done. This might include an abdominal sonogram or CT scan to look for a hidden abscess, stool cultures, an ANA (arthritis test), thyroid function tests, and antibody testing for other infections.

If all of that is normal, then testing for non-infectious causes of fever, like juvenile rheumatoid arthritis, malignancies, and inflammatory bowel disease, usually comes next.

Since your child is 'coughing a lot,' that might point to a respiratory illness as the cause of his fever, like a cold that turned into pneumonia or a sinus infection.

Walking pneumonia or mycoplasma pneumonia can cause a high fever, and may also be a possible cause of his symptoms. It is not unusual for this infection to last 1-3 weeks before a child starts to show improvement.

Again, since he isn't getting better, you should see a doctor again.

Clues to FUO Cause

To help your doctors narrow down what is causing your child's fever, consider the following questions:
  • Has he been around anyone else that has been sick?
  • Has he traveled out of the country recently? (Malaria)
  • Has he been around any farm animals or wild animals? (Brucellosis, Tularemia)
  • Do you have any pets? (reptiles - Salmonella infections, Birds - Psittacosis)
  • Has he been bitten by a tick? (Lyme Disease, Q Fever, Rocky Mountain Spotted Fever)
  • Has he been scratched by a kitten? (cat-scratch disease)
  • Has he eaten any raw or undercooked foods or drink unpasteurized milk or juice?
  • Does he have a heart murmur? (bacterial endocarditis)
  • Has he been taking any medications? (drug fever)
  • Does anything like this run in the family? (familial Mediterranean fever)
  • In addition to the fever, has he had other symptoms, like night sweats and weight loss? (lymphoma)
Again, keep in mind that since your child is 'coughing a lot,' he really doesn't haven't a fever of unknown origin, and he may just have some type of respiratory illness.

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