Aerosols spread tuberculosis like Covid-19: Study

Much like Covid-19, tuberculosis (TB) is also spread primarily by inhalation of virus-laden aerosols more than coughing, as thought so far, according to study by South African researchers.

Researchers from the University of Cape Town presented the study at the 52nd Union World Conference on Lung Health, being held online between October 19-22.

The team showed that about 90 per cent of TB bacteria released from an infected person may be carried in tiny droplets, called aerosols, that are expelled when a person exhales deeply, the New York Times reported.

The study echoes the recent findings that SARS-CoV-2, the virus causing Covid-19, along with others such as MERS-CoV, influenza, measles, and the rhinoviruses that cause the common cold all spread via aerosols that can build up in indoor air and linger for hours.

"Our model would suggest that, actually, aerosol generation and TB generation can happen independent of symptoms," Ryan Dinkele, a graduate student at the University of Cape Town who presented the results, was quoted as saying by the NYT.

However, the new study does not change that the TB transmission occurred via droplets -- a single cough can expel more bacteria than a single breath.

"But if an infected person breathes 22,000 times per day while coughing up to 500 times, then coughing accounts for as little as 7 per cent of the total bacteria emitted by an infected patient," Dinkele said.

The finding helps explain why tightly packed indoor spaces, like prisons, often are breeding grounds for TB, as they are for Covid.

Further, the study also suggested that measures used to curb Covid transmission like masks, open windows or doors, are important in limiting TB, the report said.

TB is caused by a bacterium called Mycobacterium tuberculosis, which usually attacks the lungs.

It is the world's deadliest infectious disease after Covid-19, claiming more than 1.5 million lives in 2020 -- the first increase in a decade, according to the World Health Organization's 2021 Global TB report published last week.

Covid-19 has pushed back progress made on TB as the pandemic disrupted access to healthcare and supply chains around the globe. In 2020, 5.8 million people were diagnosed with TB. But the WHO estimates that about 10 million people were infected, the report said.