Prolonged Fever of Unknown Origin
A prolonged fever of unknown origin (FUO) is simply one that lasts longer than usual, for example, more than the seven to 10 days that you would expect with a simple viral infection. Antibiotics usually aren’t prescribed just because a child has a fever that is lasting a long time. In many cases, no specific cause of the fever is found, and it just stops.
Evaluation
If your doctor sees your child within the first three to five days, they may decide to just observe your child after a full physical exam and depending on how well or sick your child seems. After that, your pediatrician will likely do more testing if the fever persists, like the strep test and blood count, depending on your child’s other symptoms. At that point, if your child still has a fever, they will almost certainly need to be seen again. This is especially important since you think your child is getting worse. If you’re not comfortable seeing your pediatrician again, then consider getting a second opinion from another pediatrician or by going to the emergency room at a children’s hospital. Further testing might include:
Blood cultureChest X-rayHIV testLiver function testsPPD to test for tuberculosisRepeat blood countSedimentation rate (ESR) and C-reactive protein (CRP) testTesting for monoUrinalysis and urine cultureViral respiratory panel
A detailed physical exam might provide further clues. The pediatrician may especially look out for mouth ulcers, rashes, swollen lymph glands, or classic symptoms of pediatric diseases such as Kawasaki disease. After several weeks of a child having FUO, more testing is 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. If normal, then testing for non-infectious causes of fever, like juvenile rheumatoid arthritis, malignancies, and inflammatory bowel disease usually comes next. Walking pneumonia or mycoplasma pneumonia can cause a high fever and may also be a possible cause of their symptoms. It is not unusual for this infection to last one to three weeks before a child starts to show improvement.
Common Causes
In addition to your pediatrician, a pediatric infectious disease specialist and a pediatric rheumatologist might be helpful if your child has a prolonged fever. To help your doctors narrow down what is causing your child’s fever, consider the following questions and possible sources of the fever:
Do you have any pets? (Salmonella infections from reptiles and psittacosis from birds) Does anything like this run in the family? (familial Mediterranean fever) Does your child have a heart murmur? (bacterial endocarditis) Has your child been around any farm animals or wild animals? (brucellosis, tularemia) Have they been around anyone else that has been sick? Has your child been bitten by a tick? (Lyme Disease, Q fever, Rocky Mountain spotted fever) Has your child been scratched by a kitten? (cat-scratch disease) Have they been taking any medications? (drug fever) Has your child eaten any raw or undercooked foods or drink unpasteurized milk or juice? Has your child had episodes like this before and were they associated with ulcers in their mouth? (PFAPA syndrome) Has your child missed any routine vaccines? (Your doctor might not think of vaccine-preventable diseases, figuring that your child should be vaccinated and protected against them) Has your child traveled out of the country recently? (malaria or other diseases) In addition to the fever, have they had other symptoms, like night sweats and weight loss? (lymphoma)
