2 Deadliest Infectious Diseases Have This in Common

Masks and better ventilation could be key in preventing the spread of the world's second-most deadly infectious disease, just as with the first. Coughing has long been thought to be the main way in which tuberculosis, which claimed 1.5 million lives in 2020, spreads from person to person. But a new study—following similar research on SARS-CoV-2, which claimed an estimated 3 million lives last year—finds up to 90% of the disease-causing Mycobacterium tuberculosis (Mtb) bacteria exuded from an infected person comes in aerosols released through breathing—a finding that could transform "decades of containment strategy focusing on coughing alone," per AFP.

Researchers knew some Mtb bacteria were released when an infected person breathed, but the level was thought to be much lower than with coughing, the dominant symptom. "Our model would suggest that, actually, aerosol generation and TB generation can happen independent of symptoms," study author Ryan Dinkele, a graduate student at the University of Cape Town who presented the not-yet-peer-reviewed findings at a virtual conference on Tuesday, tells the New York Times. Researchers tested aerosols released by 39 people with TB through regular breathing, deep breathing, and coughing. Mtb bacteria was detected within five minutes with all three.

Coughing did produce three times the bacteria of breathing, per AFP. But if a person were to breathe 22,000 times and cough 500 times in a day, coughing would account for just 7% of the total bacteria spread, the Times reports. And the smaller aerosols released through breathing stay in the air longer than larger droplets. As many people only seek treatment with the telltale TB symptoms of cough and weight loss, "this leaves room for extensive Mtb transmission prior to treatment seeking," Dinkele tells AFP. He suggests efforts be made to find early cases through aerosol testing. He notes air safety may also be improved in crowded places where TB is known to spread, such as in prisons and homeless shelters. (More tuberculosis stories.)