Fever in the Era of Coronavirus

Checking our temperature has become an essential ritual in this era of COVID-19 pandemic. No one used to care if I had fever, but now fever rules the world. Now everyone wants to know if I have fever. If I do, not only will I be denied entry to a school, office, restaurant, airplane, or a train, but I will most likely be quarantined. So, when the Wall Street Journal published an article on the subject, it gave me the idea to write about fever and thermometers.

Heat in the body is produced by metabolic activity, mostly in the muscles and the liver. It is the responsibility of the temperature regulatory center, which is in the brain (the hypothalamus) to maintain a steady temperature. Excessive heat is removed through the skin and our breath. The normal core body temperature is generally defined as 98.6 ºF (37ºC). The body temperature does fluctuate between men and women, time of the day, environmental exposure, clothing, and many other factors.

Fever, an elevation in core body temperature, is characteristic of most infections. Although fever can also occur in several noninfectious conditions such as autoimmune and auto-inflammatory diseases.

A morning reading >37.2°C (98.9°F) or an afternoon temperature of >37.7°C (99.9°F) would be considered a fever. Rectal temperatures are generally 0.6°C (1.0°F) higher than oral readings.

Most of the time, fever is not dangerous. But a person feels more comfortable at a lower temperature. A sudden change in body temperature of two degrees or more should raise concerns. Elevated core temperature increases the demand for oxygen and can aggravate pre-existing heart or lung conditions.

Our bodies need higher temperature to fight infections. That is part of the natural defense mechanism. When faced with an infection, the immune system re-sets the body’s thermostat higher. This is the same as we reset the thermostat to warm up the house. With the higher reset, the boiler turns on and the house temperature rises. The thermostat keeps it at the desired level till it is reset again. The body has its own mechanism to generate heat. Chemical signals are sent to the muscles which start to shake and shiver. Blood flow to the skin is decreased to prevent heat loss. Less flow of the blood to the skin makes us feel cold and forces us to put on extra layers of clothes and cover ourselves with blankets. Once the core body temperature reaches the desired level, the shivering stops. Higher body temperature (fever) is maintained if the infection persists.  Once the infection is brought under control, the body’s thermostat is re-set back to normal. Medicines like Tylenol, work by resetting the body’s thermostat a few degrees lower and getting rid of the fever.

We measure our body temperature with a thermometer. The word comes from the Greek words θερμός, thermos, meaning "hot" and μέτρον, metron, meaning "measure".

It is amazing how many households were caught off guard and did not have a thermometer when the pandemic started. Some friends told me that like the toilet tissue, thermometers disappeared from the store shelves, and the waiting time for the online orders was two or three weeks. 

Digital and infrared thermometers are generally considered the best, when used correctly. Disposable strips are frowned upon. Old-fashioned mercury thermometers also not in favor nowadays. By the way, the first reliable mercury thermometer was invented almost 300 years ago in 1724 by Daniel Gabriel Fahrenheit, a Dutch scientist and inventor.

Infrared thermometers can give fast, accurate readings simply by pointing at the subject’s forehead, except for babies. Babies’ blood vessels are not mature enough for infrared measurement of the forehead, and their ear canals are too small. For babies, a digital thermometer in the rectum is the gold standard.

When the instrument is used in the ear canal, readings can lose some accuracy due to wax and hair.

Digital thermometers cost less than infrared but can be hard to use for children. A digital thermometer must be kept enclosed in the mouth, armpit or rectum while staying still. If using a digital thermometer, the mouth and rectum generally produce the best results because each takes only about 30 seconds to give an accurate reading. Armpits require three to five minutes on average, so they may not be an ideal area to test for children,

On a related note: For households that use both rectal and oral options, different thermometers should be used for each for hygiene purposes. It is advised to label the different thermometers to avoid confusion. The digital thermometer can be cleaned with rubbing alcohol or soaking the metal part in hydrogen peroxide for about 25 minutes.

The source material for this article was obtained from the medical textbook UpToDate and the Wall Street Journal article by SarahNeedleman published on May 1, 2020.