Why do we get fevers when we are sick

The Curious Case of Fever: History, Function, and Modern Treatment

In 1917, doctors proposed an extraordinary treatment for syphilis, a disease that had ravaged Europe for centuries. Their method was both innovative and perilous: infect patients with malaria, a mosquito-borne illness, hoping that the high fevers induced by malaria would combat the syphilis. Afterward, they would administer quinine to treat the malaria. While this approach had a high mortality rate—about 15% of patients died—it surprisingly became a standard treatment for syphilis until penicillin was introduced decades later. This unconventional therapy underscores the crucial role of fever in the body's fight against infection.

Fever, a rise in body temperature, is a universal response found in all mammals, some birds, and even a few invertebrates and plants. This response has persisted for over 600 million years of evolution, suggesting it plays a vital role in survival. However, fever comes with a significant energy cost. For every 1°C increase in body temperature, there is approximately a 12.5% increase in energy expenditure—equivalent to about 20 minutes of jogging for some individuals.

So, how does fever work? The human body maintains its core temperature through a process called thermoregulation. This complex system is managed by the hypothalamus, a part of the brain that detects even minor temperature changes. When the body gets too hot, the hypothalamus triggers mechanisms like sweating and blood vessel dilation to release heat. Conversely, if the body gets too cold, it constricts blood vessels and induces shivering to generate heat.

When the body needs to induce a fever, it disrupts this normal temperature equilibrium. Fever sets in at temperatures above 38°C and is carefully regulated to avoid exceeding 41°C, which could cause organ damage. This increase in temperature is typically triggered by immune cells responding to an infection. These cells release chemicals that signal the hypothalamus to raise the body's "set point," thereby initiating the fever.

The primary function of fever is not entirely understood, but it is believed to be crucial in enhancing the body's immune response. At elevated temperatures, some cells produce heat shock proteins (HSPs), which play a significant role in immune function. HSPs assist lymphocytes—white blood cells that combat pathogens—by enhancing their "stickiness." This increased stickiness helps lymphocytes adhere to and pass through blood vessel walls more effectively, allowing them to reach infection sites more rapidly.

In addition to aiding lymphocytes, HSPs have other protective roles. During viral infections, HSPs help neighboring cells to reduce their protein production, limiting the virus's ability to replicate. This restriction helps to curb the spread of the virus since viruses rely on host cells' machinery to reproduce. Furthermore, by protecting surrounding cells from damage and reducing large-scale destruction, HSPs help minimize the overall impact of the infection on the body.

Despite the benefits of fever, clinical trials have shown mixed results regarding the use of fever-suppressing medications. Some studies suggest that these medications do not worsen symptoms or recovery rates. Consequently, the decision to suppress a fever or allow it to continue is often made on a case-by-case basis. Factors such as the fever's duration and intensity, the patient's overall health, comfort level, and age influence this decision.

When fever is allowed to run its course, doctors typically recommend supportive care, including rest and increased fluid intake to prevent dehydration. This approach helps the body maintain its strength and continue its battle against the infection while managing the symptoms of fever.

In summary, fever is a complex and energetically costly response that has evolved as a key component of the immune system. While its exact mechanisms are still being studied, fever's role in enhancing immune function and limiting pathogen spread is well-documented. As medical science continues to advance, understanding and managing fever remains a critical aspect of effective patient care.