The causes of fever: a defensive weapon against viruses and bacteria

Why do we get fevers? This article explains the main causes of a high temperature, and how the body protects itself.

Fever is a symptom, an alarm bell sounded when viruses, bacteria and toxins enter our body. A fever, or increase in body temperature, is a natural response triggered by the immune system. In other words, the causes therefore lie in our body's physiological response to attempted external attack, a rise in temperature that protects against unwanted visitors.

The causes of fever: the arrival of viruses and bacteria

In the absence of a fever, our body temperature fluctuates between 36° C and 37.5° C (96,8° F and 99,5° F). This is the due to the difference between the heat generated by the body and that used up by everyday activities like going to work or washing the dishes. Heat is produced by tissues such as muscle, and transported to the skin by the blood. When viruses and bacteria attack our body, the immune system, a protective network of chemical and cellular sensors, sends an alarm signal to the hypothalamus, the part of the human brain that controls body temperature.

Fever protects!

The hypothalamus is a kind of organic thermostat that increases the temperature and causes a fever when the immune system detects viruses, bacteria and toxins. When the signal arrives, the hypothalamus goes into action. The first defensive measure it takes is to use fever to create a hostile environment and prevent the germs trying to infect your body from reproducing. The second is to create an external manifestation of their presence.

41 degrees: the fever safety threshold

The hypothalamus sets a fever safety threshold of 41° C (105,8° F). When an infection causing a fever begins to subside, the temperature set by the "thermostat" decreases thanks to a process of cutaneous vasodilation and perspiration, which disperses more heat and reduces the temperature

Fever caused by flu

One of the most common causes of fever is flu, a respiratory tract infection resulting from a virus and more common in colder weather. The flu virus does not stay in the same form, but changes almost every year. The immune system is not always able to recognize it and plan the necessary defense measures.

When fever has more serious causes

If a fever does not follow its normal course and body temperature is very high, this may be caused by an infection which in turn is the result of more serious problems such as typhus, pneumonia, malaria or even a tumour, though there will be other more severe symptoms in these cases. Other types of infection that occur every year, such as familial Mediterranean fever, have genetic causes or are hereditary in nature.

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