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A febrile infant includes any child under the age of 2 months old who has a fever of 100.4 degrees Fahrenheit or higher. Fevers can be caused by bacterial or viral infections. Because infants do not have fully developed immune systems, they are more likely to get infections that adult immune systems would fight off. While fevers are most often caused by common illnesses such as colds, infants may have a more serious infection that requires medical attention. The younger an infant is, the higher the risk for serious infection. For example, a baby under 3 weeks of age is treated slightly differently than a baby older than 4 weeks of age.
Fever is an important cause for concern in infants. A baby who has a serious infection could also be lethargic, irritable or inconsolable. The baby may cough, vomit or have diarrhea. He or she may not want to eat and may sleep more than usual. Newborns typically sleep an average of 16 hours per day.
You can check your baby's temperature at home by using a medical thermometer. Doctors at Riley at IU Health recommend using a digital rectal thermometer for the most accurate results. Seek medical attention if your child's temperature is 100.4 degrees Fahrenheit or higher. If your baby’s temperature is taken through the armpit, ear or forehead, the results may be less accurate. Parents who take their child's temperature this way may want to see their child's pediatrician if the fever is near 100.4 degrees Fahrenheit.
You should not give your baby acetaminophen or any other medicine to reduce the fever before going to the doctor. These medicines can hide symptoms, leading to an incorrect diagnosis.
Diagnosis of Febrile Infants
Not all fevers in infants are caused by serious illnesses. However, doctors cannot know the cause of the fever without proper testing. Doctors at Riley at IU Health practice the best guidelines for diagnosing and treating febrile infants. Each infant with a fever is checked for sepsis through a rule out sepsis work-up. The sepsis work-up includes tests such as:
- Blood test. A blood test can reveal if your child has bacteria in his or her blood that is causing the fever. Bacteria in blood can spread infection to other areas of the body, such as the brain or bones. The results of a blood culture take 24 to 48 hours to process.
- Urine culture. A urine culture may reveal a urinary tract infection (UTI). UTIs in babies can be serious. The results of a urine culture take up to 48 hours to process.
- Lumbar puncture. During a lumbar puncture, doctors take samples of cerebrospinal fluid from the spine. The fluid is tested for bacteria and viruses such as meningitis and herpes. These serious infections can cause developmental delays, hearing loss, seizures and death if left untreated.
- Respiratory viral panel. This test uses a swab of the inside of the baby’s nose to check for certain viruses that can cause fevers, such as respiratory syncytial virus (RSV) or influenza.
Treatments
Treatments
It is routine for infants younger than 6 weeks old with a fever of 100.4 degrees Fahrenheit or higher to be admitted to the hospital while diagnostic tests are processed. The management for 6-week-old children to 2-month-old children is somewhat more flexible and based on factors such as how sick the baby appears and what is most likely causing the fever.
Depending on their exact age, most infants will also begin receiving antibiotics before test results are available. Because infections can cause serious long-term problems, treatment should not be delayed. Once results from the rule out sepsis work-up are complete, your child’s treatment will be tailored to fit the cause of the fever. He or she may receive specific antibiotics or an antiviral agent to fight the infection.
Your child will also receive supportive care, including:
- Medicines to reduce the fever. These medicines lower fevers and stabilize the heart rate and breathing to help your child feel more comfortable.
- Nasal saline and suction. If your child has nasal congestion or a runny nose, nurses may use nasal saline and suction to keep his or her nose clear of mucus.
- Oxygen through a nasal cannula. If the oxygen levels in your child's blood are low because the infection is causing breathing problems, your child will receive extra oxygen through tubes in his or her nose.
- Intravenous (IV) fluids. If your child will not eat, he or she may also receive fluids through an IV to prevent dehydration.
If your baby is doing well and all tests are negative for serious infections after 48 hours, he or she will be able to go home.
Key Points to Remember
Key Points to Remember
- A febrile infant includes any child under the age of 2 months old who has a fever of 100.4 degrees Fahrenheit or higher.
- Febrile infants require medical attention.
- Not all fevers in infants are caused by serious illnesses. However, doctors cannot know the cause of the fever without proper testing.
- A rule out sepsis work-up will test your baby’s blood, urine and cerebrospinal fluid for bacteria and viruses that could be causing the fever.
- Most babies with fevers will spend at least 36-48 hours in the hospital while awaiting test results.
Support Services & Resources
Support Services & Resources
To learn more about fevers in infants, please visit the resources below:
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
This website from the American Academy of Pediatrics includes information about fevers in babies as well as many other topics.
Febrile Infants Research
Febrile Infants Research
The Hospitalist Department at Riley at IU Health is currently participating in a pilot research project to speed up the diagnosis of serious infections. The goal of this research is to ensure the accuracy of a new blood test that may be able to reveal the cause of infections in just two hours instead of 48 hours.
If your infant comes to Riley at IU Health with a fever, you may be asked if you would like to participate in this pilot project. While your baby will still receive a rule out sepsis work-up that takes 48 hours to complete, he or she will also have the new blood test completed. If the blood test is successful, you and your child will have helped future families get answers and care faster than ever before.