At the age of 5, Robert Koch (1843–1910) announced to his astonished parents that he had taught himself to read with the newspaper. This was the first sign of the young German boy’s precocious nature. Koch later went on to become a renowned physician and scientist. In 1882, he presented a lecture on the discovery of the bacterium Mycobacterium tuberculosis, the cause of the disease tuberculosis (TB). The audience sat stunned—and, one by one, went to look at the stained slides as evidence.

M. tuberculosis is spread when someone with the disease coughs, speaks, or sneezes, diffusing microscopic droplets in the air. TB is fairly difficult to contract; in most cases, long-term contact with an infected person, such as a family member, is required. About a month after infection, the body’s immune system kicks in and surrounds the bacteria in the lungs. This can lead to latent TB, which isn’t contagious and won’t cause symptoms. In fact, although one-third of the world’s population has come in contact with the TB bacterium, 90 percent have this harmless form of the disease or have walled it off to a point where the bacteria die from lack of nutrients.

For the other group of sufferers, TB can be deadly. When the immune system fails, the TB bacteria attack the lungs and enter the bloodstream, through which the organisms can spread to other areas of the body. Symptoms include a cough lasting more than 3 weeks, bloody phlegm, chest pain, fever, chills, and weight loss. This active form of TB is contagious.

Physicians screen for the infection with the Mantoux test, in which a small amount of a substance called PPD tuberculin is injected into the skin. If a raised bump appears in 2 days, a TB infection is likely. Both the latent and the active forms of TB are treated with medication to destroy the bacteria. Because TB bacteria grow slowly, the course of medication usually lasts for 6 months to a year.

ADDITIONAL FACTS

  1. The Greek physician Hippocrates (c. 460–c. 377 BC) said something that contradicts the oath named in his honor, which binds physicians to treat anyone in need of medical attention. He warned his colleagues against seeing patients with late-stage phthisis (tuberculosis), as the patients’ inevitable deaths would stain the doctors’ reputations as physicians.
  2. Worldwide, someone is infected with M. tuberculosis every second.