What to Do If Your Child Has a Prolonged Fever

fever of unknown origin

 Verywell / JR Bee

Table of Contents
View All
Table of Contents

Having a child with a prolonged or persistent fever 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, but you also don't want to miss anything treatable or something very serious. Doctors usually use a step-wise approach when managing a child with this symptom.

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.

Fever of unknown origin (FUO) has often been defined as having a fever for three weeks or more without a known reason after one week of doctors trying to figure out the cause of the fever.


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 culture
  • Chest X-ray
  • HIV test
  • Liver function tests
  • PPD to test for tuberculosis
  • Repeat blood count
  • Sedimentation rate (ESR) and C-reactive protein (CRP) test
  • Testing for mono
  • Urinalysis and urine culture
  • Viral 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.

Coughing 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 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)
11 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Rigante D, Esposito S. A roadmap for fever of unknown origin in children. International Journal of Immunopathology and Pharmacology. 2013;26(2):3I5-326.  doi:10.1177/039463201302600205

  2. Marshall GS. Prolonged and recurrent fevers in children. J Infect. 2014;68 Suppl 1:S83-93.  doi:10.1016/j.jinf.2013.09.017

  3. Colvin JM, Muenzer JT, Jaffe DM, et al. Detection of viruses in young children with fever without an apparent source. Pediatrics. 2012;130(6):e1455-62.  doi:10.1542/peds.2012-1391

  4. Niehues T. The febrile child: diagnosis and treatment. Dtsch Arztebl Int. 2013;110(45):764-73.  doi:10.3238/arztebl.2013.0764

  5. Manual on Paediatric HIV Care and Treatment for District Hospitals: Addendum to the Pocket Book of Hospital Care of Children. World Health Organization. 2011.

  6. Rowley A, Ryan S. Kawasaki Disease. Clinician Reviews. 2013;23(2):34-38.

  7. Eken Y. Fever of unknown origin with polyarthritis. J Pediatr Care. 2016; 2:3. doi:10.21767/2471-805X.100017

  8. Cuffari C. Diagnostic Considerations in Pediatric Inflammatory Bowel Disease Management. Gastroenterol Hepatol (N Y). 2009; 5(11): 775–783.

  9. Pneumonia: Atypical (Walking) Pneumonia. Cleveland Clinic. 2015.

  10. Statler VA, Marshall GS. Characteristics of Patients Referred to a Pediatric Infectious Diseases Clinic With Unexplained Fever. J Pediatric Infect Dis Soc. 2016;5(3):249-56.  doi:10.1093/jpids/piv008

  11. Soon G. Approach to recurrent fever in childhood. Can Fam Physician. 2017;63(10): 756–762.

Additional Reading
  • American Academy of Pediatrics. Red Book: 2015 Report of the Committee on Infectious Diseases. Elk Grove Village, IL: American Academy of Pediatrics; 2015.
  • Long SS, Pickering LK, Prober CG. Prolonged, Recurrent, and Periodic Fever Syndromes. Principles and Practice of Pediatric Infectious Diseases (Fourth Edition), Part II, 2012, Pages 117-127.

By Vincent Iannelli, MD
Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.