NPR That has been the question for nearly 150 years, when Dr. Robert Koch first identified the rod-shaped bacterium that causes tuberculosis. This serious respiratory illness is currently the world’s deadliest infectious disease, killing more than a million people a year.
The most common test to determine if someone has tuberculosis hasn’t really changed since the late 1800s. The process relies on phlegm.
“It’s a nasty substance,” says Adithya Cattamanchi, a pulmonologist at UC Irvine. “No one likes it, right? You don’t like to cough it up. Health workers don’t like to work with it. It’s difficult to work with in the lab because it’s so viscous.” In addition, not everyone can produce phlegm easily, including children, the elderly and those weakened by disease.