Condition

Pediatric Fever of Unknown Origin

A fever is defined by most healthcare providers as a temperature of 100.4°F (38°C) and higher when taken rectally.

The body has several ways to maintain normal body temperature. The organs involved in helping with temperature regulation include the brain, skin, muscle and blood vessels. The body responds to changes in temperature by:

Increasing or decreasing sweat production
Moving blood away from, or closer to, the surface of the skin
Getting rid of, or holding on to, water in the body
Seeking a cooler or warmer environment

When your child has a fever, the body works the same way to control the temperature. But it has temporarily reset its thermostat at a higher temperature. The temperature increases for a number of reasons:

Chemicals, called cytokines and mediators, are made in the body in response to an invasion from a microorganism, malignancy, or other intruder.
The body is making more macrophages. These are cells that go to combat when intruders are present in the body. These cells actually "eat-up" the invading organism.
The body is busy trying to make natural antibodies, which fight infection. These antibodies will recognize the infection next time it tries to invade.
Many bacteria are enclosed in an overcoat-like membrane. When this membrane is disrupted or broken, the contents that escape can be toxic to the body. They stimulate the brain to raise the temperature.

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Frequently Asked Questions

What conditions can cause a fever in children?

What are the benefits of a fever in a child?

What are the symptoms that my child may have a fever?

Children with fevers may become more uncomfortable as the temperature rises. Along with a body temperature greater than 100.4°F (38°C), symptoms may include:

Your child may not be as active or talkative as usual.
Your child may seem fussier, less hungry and thirstier.
Your child may feel warm or hot. Remember that even if your child feels like he or she is "burning up," the measured temperature may not be that high.

The symptoms of a fever may look like other health conditions. According to the American Academy of Pediatrics, if your child is younger than 3 months of age and has a temperature of 100.4°F (38°C) or higher, you should call your child's healthcare provider right away. If you are unsure, always check with your child's healthcare provider for a diagnosis.

When should a fever in a child be treated?

In children, a fever that is making them uncomfortable should be treated. Treating your child's fever will not help the body get rid of the infection any faster. It simply will relieve discomfort linked to the fever. Children between the ages of 6 months and 5 years can develop seizures from fever (called febrile seizures). If your child does have a febrile seizure, there is a chance that the seizure may occur again. But usually children outgrow the febrile seizures. A febrile seizure does not mean your child has epilepsy. There is no evidence that treating the fever will reduce the risk of having a febrile seizure.

What can I do to decrease my child's fever?

Give your child an antifever medicine, such as acetaminophen or ibuprofen. DON'T give your child aspirin. It has been linked to a serious, potentially fatal disease, called Reye syndrome.

Other ways to reduce a fever:

Dress your child lightly. Excess clothing will trap body heat and cause the temperature to rise.
Encourage your child to drink plenty of fluids, such as water, juices or popsicles.
Give your child a lukewarm bath. Do not allow your child to shiver from cold water. It can raise the body temperature. Never leave your child unattended in the bathtub.
Don't use alcohol baths.

When should I call my child's healthcare provider?

Unless advised otherwise by your child’s healthcare provider, call the provider right away if:

Your child is 3 months old or younger and has a fever of 100.4°F (38°C) or higher. Get medical care right away. Fever in a young baby can be a sign of a dangerous infection.
Your child is of any age and has repeated fevers above 104°F (40°C).
Your child is younger than 2 years of age and has a fever of 100.4°F (38°C) that lasts for more than 1 day.
Your child is age 2 or older and has a fever of 100.4°F (38°C) that lasts for more than 3 days.
Your baby is fussy or cries and can't be soothed.

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PATIENT STORY

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Providers Who Treat Fever of Unknown Origin

Roberta Lynn DeBiasi, MD, MS

Division Chief, Infectious Diseases
Co-Director, Congenital Zika Program
Co-Director, Congenital Infection Program

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Roberta Lynn DeBiasi, MD, MS

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Nada Sami Harik, MD

Director, Fellowship Training Program
Infectious Diseases Specialist

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Nada Sami Harik, MD

Locations

Main Hospital

Departments

Infectious Diseases

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Alexandra Brugler Yonts, MD

Infectious Diseases Specialist

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Alexandra Brugler Yonts, MD

Locations

Main Hospital

Departments

Infectious Diseases

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Departments that Treat Fever of Unknown Origin

Infectious Diseases

Our Division of Infectious Diseases is the major referral center for infectious diseases in the Washington, D.C., area, helping thousands of patients each year, and actively promoting prevention through community outreach and education.