Feeling flu-ish? Five facts about fever

Fever has been in the news lately — with the nation nervously watching as airports screen travelers by checking their temperatures and as hospitals isolate feverish people who might have been exposed to Ebola.

Of course, most of those people don't turn out to have Ebola. There are many more likely explanations for a fever, including the flu, which is about to start its annual onslaught. Even in years without Ebola — or the now slowing outbreak of enterovirus D68 among children — fevers can cause outsize fears.

So, in the interest of cooling those fears and preparing you for real emergencies, here are five facts about fever:

1. A normal temperature is a range, not a number.

The body temperature of an average, healthy human child or adult is 98.6 degrees Fahrenheit (37 degrees Celsius). But that does not make 98.7 degrees a fever or 98.5 degrees a case of hypothermia. Instead, it's normal for temperature to vary a bit person to person and for an individual's temperature to go up and down by a degree or so. For example, women see temperature variations during their menstrual cycles, says Andrew Pavia, chief of pediatric infectious diseases at the University of Utah.

Doctors consider an elevated temperature to be a fever when it reaches 100.4 degrees F (38 degrees C).

2. There are many ways to take a temperature.

Old-fashioned glass thermometers containing mercury were long ago replaced by digital versions in most medicine chests (a good thing, because mercury is a hazard).

But the basic digital stick thermometer — good for oral, rectal or under-arm readings — now has plenty of competition, including more expensive ear and forehead thermometers that take temperature with infrared rays.

When used as directed, the devices provide accurate readings, says Raj Kasbekar, vice president for regulatory affairs at Kaz, which manufactures Braun and Vicks brand thermometers.

For children under age 3, it's still best to get a rectal reading with a regular digital thermometer, says Janice Sullivan, director of a clinical research facility at Kosair Children's Hospital, Louisville.

In most situations, though, the thermometer you use is less important than that you use one, says Jay Kaplan, an emergency physician in Greenbrae, Calif., and president-elect of the American College of Emergency Physicians. A hand on the forehead is not good enough, he says: "You need to actually take the temperature and document the fever."

3. A fever can have many causes.

While most people are familiar with fevers from viral and bacterial infections — everything from the flu to the norovirus stomach bugs and strep throat — fever can accompany cancer and immune disorders or be a reaction to certain medications, Pavia says.

One illness that usually does not cause a sudden high fever, however, is the common cold. If you have a sudden high fever, accompanied by shaking chills, you are likely to have a more serious infection, such as the flu, Pavia says.

Body temperatures higher than 104 degrees F can be a symptom of heat stroke — the kind of dangerous overheating associated with exercising outside on a hot day.

4. Not all fevers need to be treated.

"A fever in and of itself isn't harmful," Pavia says. "We know that in some ways a fever is a good thing. Part of the immune system works better at a higher temperature." And contrary to popular parental belief, fevers (unlike heat stroke) don't cause brain damage in children, the American Academy of Pediatrics said in a report issued in 2011. The report was aimed, in part, at battling what pediatricians call "fever phobia," says Sullivan, who was the lead author.

While anxious parents may want to treat every fever, the real aim should be making the child comfortable — meaning you should not wake a peacefully sleeping child to take a temperature or administer medication, the academy says.

If you do give a child acetaminophen or ibuprofen, it's important to follow dosing-by-weight instructions on packages, Kaplan says.

Always seek medical attention for a fever in a baby under 3 months old, Sullivan says.

5. Some fevers are highly preventable.

Many of the fevers that would otherwise arise this fall and winter could be prevented today — with a flu shot, Kaplan says. Regular hand washing, keeping your distance from sick people and staying away from others when you are sick can help prevent the spread of many illnesses that cause fevers. Although the presence or absence of a fever is not an exact measure of infectiousness for any disease, the standard advice that you stay away from work and keep your children out of school until a fever lifts is good common sense, Pavia says.