“Humanity has but three great enemies: fever, famine, and war; of these by far the greatest, by far the most terrible, is fever.”
―William Osler, MD

    In Dr. William Osler’s world of the late 1800s, doctors had not yet seen antibiotics rescue people from death caused by infectious diseases. Osler, one of the founders of Johns Hopkins Hospital routinely saw children die from meningitis, scarlet fever and diphtheria. He watched adults die from wound infections and cholera and the threat of mortal infection loomed over every surgical procedure. Fever was an unwelcome herald of trouble that often ended in death.

However, since antiquity fever was also thought to be therapeutic for some ailments of the brain, including melancholy and seizures. In the 1920s, a German psychiatrist, Julius Wagner-Jauregg, attempted to use the recurring high fevers of malarial infection to treat syphilis, then an incurable disease that eventually robbed patients of their minds and motor coordination.  Wagner-Jauregg was a eugenicist and later a Nazi sympathizer, and gave his patients malaria without their consent, but the fact that six of his nine patients recovered earned him the Nobel prize in medicine in 1927. He remains the only psychiatrist ever to be so honored in that discipline. Fever asylums popped up in many locations on both sides of the Atlantic in the 1930s, but were relegated to history by the discovery of antibiotics in the next decade.

How does the body temperature rise?

Fever begins when a “pyrogen” – some kind of viral or bacterial protein, or a protein made by the body as part of an inflammatory response — stimulates a tiny, deep part of the brain called the hypothalamus.  There, “warm sensitive neurons,” normally responsible for keeping the body temperature stable, act as if the temperature has fallen and slow their firing rates, triggering physiologic responses throughout the body that produce more heat. The incipient fever sufferer feels cold and sometimes begins to shiver. Blood vessels in the skin clamp down, sacrificing their flow to the core of the body in an effort raise the temperature. Heart and breathing rates go up, core temperature rises and the forehead begins to feel warm to the touch, even though the patient still feels chilled.

Definition of normal and abnormal body temperatures

Normal body temperatures vary over the course of the day and from individual to individual, within a degree above or below 98.6°F (37°C). Oral temperatures are about a degree lower than ear and rectal temperatures.  Fever is defined in adults as 100.4° orally or 101°F (38.3°C) rectally, and 101° orally in children. These elevated temperatures seem to work, along with the body’s immune system, to undermine the success of an invaders like viruses and bacteria……up to a point. Temperatures rising to 103-104° begin to have deleterious effects on cells, making their membranes unstable and triggering faults in the workings of cellular machinery. Organ failure can result, complicating already serious illness with kidney and liver problems.

Why do babies and little children get fevers so often?

Babies and small children, who are at the beginning of their life experience with infections, develop fevers more often than adults do. Their fevers may be the first or only symptoms of illness, and the illness may be brief and self-limited. Fevers which indicate worrisome problems in children are accompanied by other symptoms like rash, stiff neck, lethargy, breathing difficulties or abdominal pain.

Adult fevers 

In adults, other symptoms of trouble often come before a fever and point to a body part in some kind of trouble.  When fever occurs along with GI symptoms like abdominal pain, nausea, vomiting and diarrhea, a significant abdominal problem requiring medical or surgical attention may be present. Fever along with cough and sputum production may mean a bacterial pneumonia. Fever that develops as a part of the flu is usually accompanied by profound fatigue, muscle aches and pains and headache.

What causes fever?

About 75% of elevated temperatures come from infections. What causes account for the other 25%?  This “non-pyrogenic category” includes fevers from some cancers, from inflammation of all kinds, from brain injuries like hemorrhages and strokes, and from major bodily injuries with crushed or otherwise damaged tissues. In addition, overactive thyroid glands elevate body temperatures. Some drugs, particularly the neuroleptics used for depression and other psychiatric disorders can cause fever, as can some genetic problems.  Familial Mediterranean Fever comes from mutations in genes that control inflammation responses. Malignant hyperthermia, a potentially fatal rise in temperature in response to anesthetics, comes from a muscle gene mutation.

To treat or not to treat fever?

Treatment of fever is straightforward – body temperature drops in response to an antipyretic drug such as acetaminophen (Tylenol) or aspirin. But fever appears to be an evolutionary response in almost the entire animal kingdom, aimed at protecting the body from invasion by other living forms. In other words, fever induced by infection may be helpful.  Why try to normalize the temperature during the illness?

Most of the time, with temperatures in the 101-102 range, treatment beyond making the patient comfortable is not necessary. But the deleterious effects of raising body temperature begin to show up in the 104 range, and perhaps sooner in people who have underlying medical problems that affect their ability to tolerate higher heart and breathing rates or to maintain adequate hydration. Fever makes demands upon the body that young and otherwise healthy people can tolerate, but older, sicker people may not. Elevated temperatures in heat stroke from a hostile environment or from excessive exertion without adequate hydration serve no useful purpose and should always be treated promptly, with external cooling and hydration.

In the modern age of medicine, antibiotics have reduced Osler’s greatest enemy to a symptom of illness. But it is a symptom that deserves respect. When fever is present, something is wrong and the wrong thing usually involves and invasion of the body by another living form, or a significant area of tissue inflammation or decay. Careful evaluation of other symptoms is the first priority in discovering the cause of fever, for that is what needs treatment more than the fever itself. Should we overuse antibiotics and render them ineffective against our most common infections though, Osler’s great enemy will regain its fearsomeness.