6 Common Causes of a High Fever | The Survival DoctorPart 4 in our 4-part series on fever

by James Hubbard, MD, MPH

If you get a high fever and don’t know what’s causing it, you go to the doctor, right? But, of course, if you’ve read this blog much, you know I’m all about what to do when you can’t get to a doctor.

In either case, the first step in treatment is to know what you’re treating.

If you think infection is causing the fever (as opposed to heat exhaustion or something rare, like a tumor), often you know, in general at least, what’s causing it by what’s bothering you—for example, an infected leg, a sore throat, a stiff neck, etc. But sometimes, that’s not the case. And children may not be able to tell you what’s bothering them.

When that happens, here are six of the most common causes of high fever to consider.

1. Viruses

With a virus, the fever can be high (as with the flu) but usually runs around 101 to 103 F orally. Muscle aches and weakness are common.

Unless there’s a rash that reveals what the virus is or it’s the flu or herpes simplex, we usually don’t make a specific diagnosis other than “viral syndrome.” That’s because even if there are other tests, they’re expensive and invasive, and the treatment—fluids, rest, and tincture of time—is not going to change.

2. Strep Throat

The typical fever with strep throat goes up in the evening and lasts three days minimum, even with antibiotics. If your child has a bad sore throat with a fever, getting a strep test can be useful. (There’s no other way to diagnose it accurately.)

Where to Get Antibiotics

Sometimes, there’s just not much to do for a bacterial illness unless you have antibiotics. Learn more about antibiotics for use during disasters—including how to get them in advance—in my free report, “The Survival Doctor’s Ultimate Emergency Medical Supplies.”

Strep is a bacteria and can be treated with antibiotics. If not treated it may go away on its own, but you’re risking rheumatic fever (which can cause a prolonged illness and permanent heart damage). Proper treatment of strep with antibiotics can prevent this.

3. Ear Infections

Many ear infections are caused by viruses and go away on their own, but some are bacterial. If there’s a high fever, the infection is usually pretty bad and it’s time to see a doctor if at all possible. In those cases, antibiotics can help. You can find more about this here.

4. Urinary Tract Infections

Clues are a strong urine smell, discomfort when urinating, and abdominal pain. Antibiotics are usually beneficial. A high fever is a red flag that a true kidney infection is getting into the bloodstream (pyelonephritis) which may require IV antibiotics.

5. Meningitis

If a younger child can’t be consoled—maybe even gets worse with holding—or an older child, or adult, has a severe headache or stiff neck (not just tender lymph nodes), meningitis is a possibility, and the person should be seen by a doctor right away, even if it’s difficult to get to one. There’s not much you can do at home for this dangerous viral infection except hope that it runs its course without serious complications.

6. Pneumonia

A child usually will be breathing hard and fast. An adult is normally at least a little short of breath. A common starting symptom in adults is a shaking chill as the fever goes up (you actually shake), followed later by profuse sweating as the fever comes down. In children, if the child is young and the breastbone retracts with inhalation that’s a sign things are getting very serious and the child need supplemental oxygen.

Antibiotics may or may not help, depending on whether the cause is viral or bacterial. If I suspect pneumonia, from listening to the chest or doing a chest X-ray, I start people on antibiotics since it’s hard to tell the difference. Often, an IV is required to maintain hydration. Learn more about pneumonia here.


Now, unfortunately, viruses and bacteria can’t read. They don’t know they’re always supposed to cause specific symptoms.

For instance, when I had pneumonia, I ran a high fever and had a slight cough. I thought I had the flu. One of my colleagues examined me and suggested a chest X-ray, just to be safe. Good thing. It showed the pneumonia.

So, bottom line is, if someone has a high fever, get checked by a doctor as soon as you can.

What about you? What caused your or someone you know’s most recent high fever?


Read the entire fever series: