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The Meaning of Fever

Dr. Rick Place

Dr. Rick Place is Medical Director of the Pediatric Emergency Department at Inova Children’s Hospital (at Inova Fairfax Medical Campus in Falls Church, VA). Dr. Place is a board certified physician in both Emergency Medicine and Pediatrics.

Of all childhood afflictions, fever likely represents the most commonly feared condition in young children. By far, it is the number one reason for visiting the emergency department – at all hours of the day.

Why are we so worried about fever and what does it represent?

Historically, fever was a sign of a potentially life-threatening illness: In the pre-antibiotic era, children actually died – not of fever, but whatever caused the fever. These societal memories still in our cultural memory and instill fear in parents today.

When to seek immediate medical attention:


Child up to 6-8 weeks of age: Temperature above 100.4ºF (38ºC)


Child over 3 months of age: Temperature above 102ºF (39ºC) (Evaluation can generally be deferred until the next day as long as the child is not excessively ill appearing.)

While fever in the modern era almost always indicates infection, except in high-risk groups – immunocompromised children, neonates and young infants – fever is much less likely to represent a serious medical threat in the otherwise well-appearing child. The routine vaccinations, such as Prevenar and HiB that your children receive today, were not available in the recent past and have dramatically reduced the risk of meningitis and serious bloodstream infections that were so devastating only a single generation ago.

So what exactly is a fever?

mom taking child's temperature

There are two ways to look at this. A fever can be defined as the symptom of anyone with an elevated temperature. However, for medical providers, a “fever” is a number beyond which we believe there is an increased risk of a serious bacterial illness. For newborns between birth and 3 months of age, this is a rectal temperature over 100.4ºF (38ºC). Beyond this temperature, at this age, fever represents a possible bacterial infection and warrants urgent or emergency medical evaluation.

ANY child up to 6-8 weeks of age with a temperature above 100.4ºF (38ºC) should immediately be seen and evaluated by a medical provider. Beyond this age, we recommend contacting your primary care provider for advice on whether to seek immediate evaluation or wait for office hours.

For children over 3 months of age, a “fever” representing increased risk is generally recognized to be above 102ºF (39ºC). Historically, there has been increased risk of serious infections in 3-36 month old children but fortunately this is the age group that has been most positively impacted by vaccinations. The risk of a threatening infection in this age group is much lower now and evaluation can generally be deferred until the next day as long as the child is not excessively ill appearing.

Why do parents bring their children to the emergency department?

Interestingly, the reason parents give for visiting the emergency department is not simply the presence of fever. It is fever and something else. It might be the fact that Tylenol or Motrin are not effectively reducing the fever or that the fever is perceived to be excessively high – or has never been that high in the past. Some kids have shaking chills that are alarming to observe, as well as the decrease in appetite and activity that accompany it.

The reasons are numerous, but not all of them are issues requiring immediate evaluation. In the past, the height of the fever was an indication that a more serious illness might be causing the fever; while this is still true to a slight degree, the relationship between how high a fever is and the likelihood of a serious infection is much weaker than it once was. As for fevers that do not respond well to fever medicines – by itself, this is not an indication that the infection is more serious. Chills are common just before the fever spikes (just as sweats result from a breaking fever), but they do not suggest need for an immediate evaluation. And just to be clear – fever does NOT cause brain damage at any height.

So who needs emergent evaluation in the emergency department versus urgent evaluation at the doctor’s office the next day?

ALL clearly ill-appearing children should be seen emergently. It is understood that children with fevers will look like they do not feel well. Please remember the last time you had a fever; you might have stayed in bed and looked like you didn’t feel well too! That is expected. But if they look acutely ill, particularly if they do not look better after fever medications have been given, they should be seen emergently in the emergency department.

Young infants 8-12 weeks of age are at a transitional age. For temperatures above 100.4ºF, parents should contact the primary care doctor for advice on whether to come to the ER or wait to see them in the office the next day.

Any newborn younger than 8 weeks of age should be seen emergently for a temperature (preferably rectal) over 100.4ºF (38ºC) regardless of how well they are. Almost all of them will undergo laboratory testing.

Children over 3 months of age with fever over 102ºF (39ºC) can generally wait to be seen by the pediatrician the next day….unless they are acutely ill appearing, in which case they need to be seen emergently.

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