Tuberculosis

What Is It?

Published: January, 2019

Tuberculosis is a bacterial infection that kills approximately 1.5 million people a year. Most of these deaths occur in developing countries. The bacterium that usually causes tuberculosis in humans is Mycobacterium tuberculosis.

About one-third of the world's population is infected with tuberculosis. However, most do not show signs of the disease. In these people, the bacteria are inactive (latent) and cannot be transmitted to others. If the body's immune system weakens, tuberculosis can become active and cause disease.

To continue reading this article, you must log in.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise

New subscriptions to Harvard Health Online are temporarily unavailable. Click the button below to learn about our other subscription offers.

Learn More »