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Fever is a good thing
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| Desert iguana (courtesy of Pete Zani) |
Fever is an increase in body temperature due to infection. Since it is commonly believed to be a detrimental condition, people with fevers take drugs and other measures to decrease their temperatures as quickly as possible. Maybe the drug companies, in an attempt to market their fever reducing products, have successfully portrayed fevers as harmful situations. Despite fever's negative publicity, would you believe that a fever, when not too high, is usually a beneficial condition?
How do we know that this apparently far fetched idea is legitimate? Ask the lizards! They know from experience. This idea was confirmed through an experiment on them. After a group of desert iguanas (see picture above) were infected with bacteria, some of the lizards were allowed to get a fever. Many lizards regulate their body temperature behaviourally, for instance by seeking shadow when too hot and sunshine when too cool. By such behaviour, these infected lizards "chose" to increase their body temperature, i.e. to get themselves a fever. The rest of the lizards were prevented from getting a fever. The group of lizards who got a fever had a higher rate of survival than the group who did not get a fever. From this and other experiments, it can be concluded that fever seems to be a protective condition.
To clarify the protective role of a fever, the mechanism responsible for the temperature elevation must be understood. When you are infected with a virus or a bacterium, your white blood cells send chemicals to the brain telling it to increase the set point of your body temperature, i.e. to reset the body "thermostat" to a higher temperature. Body temperature is then raised to the new set point through increased heat production and improved heat conservation. Before you have increased your body temperature to the new set point, you feel cold. The function of increasing body temperature is probably to establish an environment in which your immune system can respond more efficiently. Once you have defeated the infective agent, the set point is returned to normal. You then return your body temperature to the normal set point through sweating and other methods of increasing your heat loss. Before body temperature has been lowered to the new set point, you feel hot.
So, rather than being the cause of infection, fever is good because it is helps the body to fight and getting rid of the infection. However, the pharmaceutical companies are not completely misleading. Fevers that get too high can be dangerous, and in such cases fever reducing drugs must be used.
References
R.W. Hill and G.A. Wyse: Animal Physiology (2:nd edition, HarperCollins, 1989).
A. Vander, J. Sherman, and D. Luciano: Human Physiology: The Mechanisms of Body Function (7th edition, WCB/McGraw-Hill, 1998).
P.C. Withers: Comparative Animal Physiology (Saunders College Publishing, 1992).