Everything Is Tuberculosis: The History and Persistence of Our Deadliest Infection

by John Green

M. tuberculosis grows so slowly because it takes a long time to build its unusually fatty, thick cell wall, which is a formidable enemy to the immune system. White blood cells struggle to penetrate the cell wall and kill the bacteria from within. In fact, it’s so hard for infection-fighting cells to penetrate the bacteria’s cell wall that, instead, white blood cells usually surround it, creating a ball of calcifying tissue known as a tubercle.[*3] The TB bacteria can survive within these tubercles, replicating very slowly, consuming dead tissue as food. This type of infection, sometimes known as latent tuberculosis, will often last a lifetime without ever making a person sick. Most people infected with TB will never become ill because the tubercles will continue to hold the bacteria within them, preventing active disease from developing. But in 5 to 10 percent of infections, the immune system can’t produce enough white blood cells to surround all the bacteria with tubercles, and M. tuberculosis is able to grow and grow within the lungs or elsewhere. The body is slowly overwhelmed by infection (and the immune system’s resulting inflammation), eventually leading to death.