Many of us have experienced bouts of fever following a viral infection such as the flu or, since the start of the pandemic, COVID-19.
Have you ever wondered, like Nicolas, a 14-year-old from Dieppe, why there is such a small difference between normal body temperature and that of a feverish person? Why is this difference enough to make us feel so bad during a fever episode?
To find out, Dr. Ghislain Lavoie, president of the New Brunswick College of Family Physicians, agreed to speak with Question de science.
The hypothalamus, the body’s thermostat
To understand why we have a fever, and what makes it make us feel bad, we must first know how our body manages to maintain body temperature.
No matter what environment you find yourself in, the human body’s thermostat, an area of the brain called the hypothalamus, is set at around 37 degrees Celsius.
It is this structure that monitors the temperature of our body through numerous thermoreceptors located in various places, especially on the surface of the skin.
When these thermometers show a temperature below 37 degrees, the hypothalamus activates, for example telling our muscles to tremble in order to warm us up. Conversely, if it’s too hot, the thermostat kicks in to trigger perspiration, one of the many mechanisms at our disposal to cool us down.
“During the day, the temperature varies a little, but the thermostat is set at a normal temperature and the functions of the body act so that the temperature remains close to the value of the thermostat”, explains Dr. Ghislain Lavoie.
In response to danger, fever
When we are exposed to a potential danger, for example during a bacterial or viral infection, the cells of our immune system sound the alarm, in particular by producing cytokines. These will act as messengers to deliver a message to the hypothalamus, which in turn will produce a hormone, a form of prostaglandin, capable of increasing the value displayed by the thermostat, which induces fever.
“Rather than being set at 37 degrees Celsius, the thermostat says the temperature should be increased to 38 or 39. The body will react because the body temperature does not match the thermostat value, so the metabolic activity will increase, there will be a decrease in the diffusion of heat through the skin, all this to raise the temperature.
This is also what explains the feeling of being cold when we are feverish. The chills and tremors of our muscles associated with the fever aim to warm us up to bring the body temperature from 37 degrees Celsius to the new value set by the hypothalamus, usually above 38 degrees.
A defense mechanism
Although fever is poorly understood by scientists, the hypothesis is that an increase in body temperature allows us to better defend ourselves in the event of an infection.
“We are not 100% sure, but it is believed that increased heat has the potential to limit the production and growth of viruses and bacteria, while increasing the efficiency and speed of our immune response. “says Dr. Lavoie.
If fever has the advantage of protecting us once morest an attacker, it also has the effect of making us feel unwell. The increased metabolic activity of the body induced by fever leads to greater consumption of oxygen and production of carbon dioxide by our cells. The heartbeat and breathing speed up.
“All of this puts stress on the body and so you feel bad. As soon as the thermostat says that the temperature is set at 38 or 39 degrees rather than 37, it’s an abnormal state for our body, it’s not used to it, so it’s a temperature difference enough to feel bad ” , explains Ghislain Lavoie.
