Fever is one of the most recognizable symptoms of COVID-19. We’ve all seen the videos of people with a thermometer pressed to their foreheads as they attempt to enter a hospital or board an airplane. It is also the most common symptom, affecting up to 87.9% of those afflicted with COVID-19, according to the World Health Organization (WHO). In fact, fever is a more common symptom of COVID-19 than a dry cough or fatigue.

That said, not everyone who has a fever will test positive for the coronavirus. Nor will everyone who has the coronavirus develop a fever.

While a coronavirus fever is very similar to any other virus-induced fever, there are some crucial differences.

Although a fever is a signal that the body is fighting off an infection, a coronavirus fever is very different in both how it should be treated and how it manifests itself. In a coronavirus patient, a fever can be a severe early warning signal and provide the first clue that the virus is present.

Here is what you need to know about fever and the coronavirus.

Diagnosing a Fever

The Centres for Disease Control (CDC) identifies a fever in an adult to be anything over 100.4 degrees Fahrenheit on an oral thermometer and over 100.8 degrees Fahrenheit on a rectal thermometer. Some of the symptoms that can, but do not always, accompany a fever include:

  • Sweating
  • Chills and shivering
  • Headache
  • Muscle aches
  • Loss of appetite
  • Irritability
  • Dehydration
  • General weakness

A thermometer is the most reliable method of assessing a fever. However, the CDC will also diagnose a fever if someone feels hot to the touch, reports feeling feverish or chilled or is flushed or glassy-eyed. To check for a fever, press your fingers against your own skin and then against the possible fever sufferer's skin to see if they feel notably warmer. These methods, however, are typically unreliable and inexact, and it is always better to use a thermometer if one is available.

Not All Fevers Are Alike

The fever associated with the coronavirus, and in fact, any fever, is not as simple to diagnose as one might think. This is especially true for a low-grade fever, which is what most coronavirus patients typically start with.

For starters, the average core body temperature of a healthy individual is typically 98.6 degrees Fahrenheit (37 degrees Celsius), but that isn’t the case for everyone. Some people, like CNN anchor Chris Cuomo, have a core body temperature that is much lower. Cuomo, who has been unable to shake his fever even several weeks after his diagnosis, has a core body temperature that is almost 1 degree lower. So what might be a low-grade fever in others can be very serious for him. Many people have this same issue.

Several other factors can affect your body temperature. Time of day can cause temperature readings to fluctuate, as can age, sex, activity levels and even, for women, the menstrual cycle.

Characteristics of a COVID-19 Induced Fever

If you think you have a fever, or may have a fever, take your temperature later in the day. With most viruses, including the coronavirus, you may be fever-free in the morning, but your temperature could spike in the late afternoon or evening.

However, the coronavirus fever is even more complicated. With other viruses, fevers usually appear fairly quickly after a person becomes infected. It’s a signal to you and your body to rest and allow yourself to get better.

With a coronavirus infection, fever may not appear for four to six days and could also take up to two weeks. If no other symptoms are present, you may be at risk of infecting others for several days before you know you are actually sick. In fact, some studies are suggesting that a person with the coronavirus is most infectious two or three days before the onset of any symptoms. A fever is also not necessarily the first symptom that appears with coronavirus, although it is for many.

Occasionally the fever associated with the coronavirus is below 100 degrees Fahrenheit. If you think you have a fever or may have been exposed to the coronavirus, take your temperature in the morning and evening and keep track of these measurements for fourteen days. If you are experiencing other symptoms or are concerned, contact your health care provider or local hospital, who can advise you or may suggest testing.

Complications with Fevers

Under normal circumstances, fevers can be allowed to run their course and do not have any severe or long-term effects on individuals. However, sustained high fevers, those that are at or above 103 degrees Fahrenheit, can lead to seizures or brain damage. If you are worried about a persistent fever, you should contact your health care provider.

How to Treat a Coronavirus Fever

It isn’t necessary to treat a fever unless you are uncomfortable. Cool cloths can help cool you down. Drink plenty of liquids to avoid dehydration and use warm blankets to stave off the chills.

If your fever is making you uncomfortable, however, you can take medication to reduce it. Both acetaminophen, commonly known as Tylenol, and anti-inflammatory drugs such as ibuprofen (Advil) and naproxen (Aleve) work to reduce fevers.

There was a concern early in the pandemic that that anti-inflammatory drugs could make the coronavirus worse. However, both the CDC and the World Health Organization (WHO) have declared these drugs safe to use to reduce fevers associated with COVID-19.

When to Seek Help

Both the CDC and the Mayo Clinic, among others, have created self-assessments for COVID-19 that can help you evaluate your symptoms, including fever. The WHO also has extensive advice about dealing with coronavirus in a variety of circumstances.

The bottom line is that if you are concerned about your symptoms or exposure to the virus, you should first contact your health care provider or access the information on your state, county or city department of health pages.

Remember that this is a new pandemic, and new studies and treatments are appearing almost daily. Be sure to get the latest advice from trusted sources.