(This article is part of a series of articles on tuberculosis that I wrote for the Summer 2008 issue of NYU Physician.)

WHITE PLAGUE. KING’S EVIL. WASTING disease. Phthisis. Consumption. Tuberculosis (TB) is an old disease with many names and guises. But it wasn’t until last year that scientists discovered how old this ancient scourge really is. Egyptian mummies, skeletal remains, and genetic analysis had all suggested that TB had been around for at least a few thousand years. But in a block of rock mined from a quarry in Western Turkey, anthropologists discovered the fossil of a young male dating back some 500,000 years and infected, unexpectedly, with tuberculosis. They announced in December 2007 that the young man had lesions on the inside of his skull, the imprint of brain membranes that the disease has been ravaging humans for much longer than anyone had ever suspected.

An estimated 2 billion people — nearly one-third of the world’s population — are thought to harbor Mycobacterium tuberculosis (M. tb), the bacterium that causes TB. It grows slowly, lurking in the lungs for years, and outwits the body’s immune system, in part by waiting for the host’s defenses to weaken. In most people, that opportunity never arises, and they show no symptoms of the disease. But once M. tb takes hold, it literally consumes the body from within, eating through lung tissues and the blood vessels that run through it. Every time someone with a full-blown infection speaks, sings, coughs, or sneezes, the bacteria expelled linger in the air for hours, ready to invade the next victim.

This is why TB has so often been a disease of the poor, because it is at its most deadly in overcrowded, unsanitary conditions. In 2006, TB infected 9.2 million people worldwide, claiming the lives of 1.5 million people, most in the developing world. In some parts of South Africa, as many as 70 percent of those with TB are also infected with HIV, because TB is opportunistic.