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COVID-19 is running rampant throughout the globe. Contagious and sometimes deadly, it’s likely to cause severe illness in millions and ruin economies before it’s done.

You probably know the classic symptoms: Fever (also known as “pyrexia“) occurs in 88 percent of cases, followed by a dry cough. One in five or six go on to develop pneumonia. Of these, a percentage will succumb to the disease. You should know about these symptoms and others associated with COVID-19 and other infections. Today we’ll discuss fevers.

Why do we get fevers when we’re sick? There seems to be a body of evidence that suggests a higher body temperature kills many viruses and bacteria that do just fine at a normal temperature (98.6 degrees Fahrenheit). Fever is a weapon against disease-causing organisms.

What constitutes a fever? An elevated body temperature, of course, but how high? In medical school, I learned that it wasn’t a fever until you hit about 100.4 degrees Fahrenheit. This equals 38 degrees Celsius. In older people, the immune system is often too weak to mount that high a temperature. Any elderly person at 99.6 or so should be considered as “febrile” (having a fever).

Your temperature is a fluid statistic, however. In the morning, it is lower than it is in the late afternoon or evening, sometimes by a degree or more. The temperature also varies dependent on the method used to measure it.  

In the past, people used mercury thermometers. These were made of glass and required no battery, a useful item long-term off the grid. Unfortunately, they could break, causing cuts and dispersing mercury (a toxic substance).

Today’s thermometers are electronic and non-toxic. There are various types on the market that use the mouth, armpit, rectum, ear, and forehead. Compared to the standard normal oral temperature of 98.6 degrees, you can expect:

  • A normal armpit reading to be one half to one degree lower (97.6)
  • A normal rectal temperature to be one half to one degree higher (99.6)
  • A normal temperature using an ear thermometer to be one half to one degree higher (99.6)
  • A normal forehead scanner (such as those used in many airports) temperature to be one half to one degree lower (97.6)

So, if a person’s temperature is 100.4 F orally, it could be 99.4 in the armpit or forehead and 101.4 in the rectum or ear. Rectal temps are thought to be most accurate, while armpit temperatures are thought to be least accurate.

Note: An oral thermometer reading may be inaccurate if you ate or drank something recently. A precise value may not be obtainable for 15-30 minutes afterwards.

The ability to use the thermometer properly is an important factor. This isn’t difficult for adults that read the instructions, but a fussy, sick toddler may not cooperate. In this case, a rectal temperature reading may be the most accurate.

Many use the ear thermometer. This is also known as a tympanic thermometer, named after the tympanic membrane or “eardrum”. Tympanic temperature readings average about the same as rectal. To be accurate, take the temperature in both ears and use the highest reading. The reading may be artificially elevated if you have been laying on your side with your ear on a pillow. As well, it’s said that those with a very short, curved ear canal may not have reliable results. This is a tough one to tell unless you ask your doctor to take a look during an exam.

“Forehead” thermometers actually scan the temperature of the temporal artery. This item is superior to forehead strips, which are better at measuring skin temperature than body temperature. Be aware that they can be expensive.

Here’s advice from Seattle Children’s hospital on how to properly use each type of thermometer:

Rectal Thermometer

If taking a temperature on a infant or small child, have them lie stomach down on your lap or on their back with the legs pulled up. Put some petroleum jelly on the end of the thermometer and, also, the anus. Gently slide in the thermometer no more than 1 inch; For infants less than 6 months old, no more than ½ inch. This is usually the point where you no longer see the metallic tip. Stop if you encounter any resistance. Leave in until it beeps (usually, about 10 seconds or so).

Armpit Temperature

After making sure the armpit is dry, put the tip of the thermometer in and hold the elbow against the side of the chest. The tip of the thermometer must be covered by dry skin and should point towards the head. It may take up to a minute (or until it beeps) to get a reading.

Oral Temperature

Oral temperatures are used in those four years of age or older. Put the thermometer under one side of the tongue towards the back. It’s important to put the tip in the right place. Have the patient hold the thermometer with their lips and fingers. Don’t use the teeth to keep in place. Keep the lips closed until it beeps (about 10 seconds).

Ear Temperature

An ear temperature can be taken at 6 months and older (not accurate before 6 months). This thermometer reads the heat waves coming off the eardrum. A correct temp depends on pulling the ear backward. Pull back and up if over 1 year old. Aim the tip of the ear probe between the opposite eye and ear. It usually takes just a few seconds for an accurate reading and is not uncomfortable for the child.

It’s important to note that being outdoors in the cold can cause an artificially low reading. The patient should be inside for at least 15 minutes before taking a temperature.

Forehead (Temporal Artery) Temperature

This thermometer reads the heat waves coming off the temporal artery. This blood vessel runs across the forehead just below the skin. Place the sensor head at the center of the forehead and slowly slide towards the top of one ear, keeping contact with the skin at all times. Stop at the hairline of the side of the head. Some of the newer versions don’t require this motion and can be placed directly on the side of the head above the ear or on the forehead.

Febrile or not, COVID-19 patients should wear a mask (and so should anyone else out in public)


Fever does not necessarily need treatment unless the patient is very uncomfortable. Fever rarely rises to a dangerous level (known as “hyperpyrexia“). Permanent damage to the brain rarely occurs below 42 degrees Celsius (107.6 degrees Fahrenheit). Untreated, a fever almost never goes about 105 degrees Fahrenheit or so.

With regards to COVID-19, I have seen reports about ibuprofen, naproxen, and even acetaminophen being withheld due to controversial reports claiming that they cause more inflammation. The hard data is not there yet to prove any of these, but non-pharmaceutical interventions such as damp cool sponges can be used for comfort purposes. It may be best to allow the fever to fight the disease if the patient can tolerate it..

Fever is an important mechanism to help you resolve an infection and also follow the course of the illness. Hopefully, the fever will break and your patient will go on to full recovery.

Joe Alton MD

Dr. Alton

Learn more about viral diseases in the Alton’s latest book “Alton’s Pandemic Preparedness Guide“, now available on Amazon and at store.doomandbloom.net.

Hey, don’t forget to check out our entire line of quality medical kits and individual supplies at store.doomandbloom.net. Also, our Book Excellence Award-winning 700-page SURVIVAL MEDICINE HANDBOOK: THE ESSENTIAL GUIDE FOR WHEN HELP IS NOT ON THE WAY is now available in black and white on Amazon and in color and color spiral-bound versions at store.doomandbloom.net.

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