The Next Big One: Drug-Resistant Airborne Tuberculosis

Even prior to the Covid-19 pandemic, there has been much discussion of what will be the next big pandemic and how do we prepare for it. New research has found that tuberculosis bacteria can spread via airborne and asymptomatic transmission similarly to SARS-CoV-2. This finding upends the conventional wisdom that coughing was the main route of transmission. It is these two characteristics that make SARS-CoV-2 so dangerous. Therefore I believe the next big pandemic might well be drug-resistant tuberculosis.

The pre-print study from South Africa has found that greater than 90 percent of tuberculosis bacteria released from an infected person may be carried in aerosols that are expelled when a person breathes out. Aerosols released from normal breathing will also linger in the air for longer than droplets released from coughs. Study co-author Ryan Dinkele told the New York Times “if an infected person breathes 22,000 times per day while coughing up to 500 times, then coughing accounts for as little as 7 percent of the total bacteria emitted by an infected patient”.

Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis, which usually attacks the lungs. The researchers were concerned about how diagnosis and treatment of tuberculosis had changed very little over the decades and sought a better understanding of how Mycobacterium tuberculosis aerosolizes and transmits. With South Africa (a high burden tuberculosis country) reporting that nearly 60% of individuals with bacteriologically confirmed pulmonary tuberculosis were asymptomatic. The researchers were particularly intrigued by how transmission occurs in these asymptomatic cases that were cough-independent.

The researchers developed a platform combining non-invasive bioaerosol capture technology and fluorescence microscopy to accurately measure the viable Mycobacterium tuberculosis released by confirmed tuberculosis patients. They created three separate respiratory scenarios for comparison, including Tidal Breathing, otherwise known as restful breathing, Forced Vital Capacity, in which the person takes the maximum inhale and exhale they can and Cough. Viable Mycobacterium tuberculosis bacilli were detected in 66%, 70%, and 65% of Tidal breathing, Forced Vital Capacity, and Cough samples respectively. While coughing increases particle aerosolization compared to Tidal breathing, this was not associated with increased Mycobacterium tuberculosis aerosolization. Instead, Tidal breathing produces more Mycobacterium tuberculosis per particle than coughing. If we assume the number of viable Mycobacterium tuberculosis organisms detected provides an accurate measure of patient infectiousness, Tidal breathing could be considered the main route of tuberculosis transmission.

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Originally published on Forbes on Oct 28, 2021 

© William A. Haseltine, PhD. All Rights Reserved.