Simple Breathing Can Transmit TB More Effectively than Cough – New Research Debunks Old Convictions About Transmission   
Researchers describe new findings about TB transmission and diagnosis tools, on the first day of the 52nd Union World Conference on Lung Health

New research published at the opening of the 52nd Union World Conference on Lung Health has demonstrated that routine breathing can transmit tuberculosis even more effectively than coughing – in a finding that also echoes one of the signature lessons from the COVID-19 pandemic about SARS-CoV2 transmission. 

While large droplets jammed with bacteria produced by coughing has long been assumed to be the main course of TB transmission – the new study published on the pre-print server bioRxiv, demonstrates how even more TB bacterium, like COVID, may be transmitted by tinier aerosol droplets released during the course of natural breathing. 

The study by a team of University of Cape Town researchers was just one of a number of new findings released at the opening day of the iconic Union conference – which is meeting virtually for the second year in a row. 

Other new findings released in the first day of the three day, global event (19-22 October)  include a new gene-based blood-prick test for initial TB screening – particularly useful for children who do not produce sputum-filled coughs; and the use of face masks to capture, and screen for, TB and multi-drug resistant tuberculosis (MDR-TB)  as yet another novel diagnostic tool.   

But it is the new study on aerosol TB transmission that is one of the most revolutionary – challenging the fundamental dogmas around TB transmission. Using sensitive measurement devices, the study documents how so-called ‘tidal breathing’ – routine inhalation and exhalation by a TB-infected person – will typically release over 90% TB bacteria (Mycobacterium tuberculosisMtb), over the course of a routine day – as compared to only 7% by coughing. 

That’s partly because an infected person will simply breathe many more times  – some 22,000 times in fact, as compared to about 500 coughs.  In contrast to the large droplets released by a cough, most of the bacteria released by breathing are in the form of tinier aerosols, which can remain suspended in the air and travel much further as well. 

Findings on Aerosols Echo lessons from SARS-CoV2 – But Research Preceded the Pandemic 

The signature findings echo lessons learned from the COVID pandemic – where the big aerosol transmission risks of SARS CoV2 have now been well acknowledged – despite fierce resistance among some experts – including at the World Health Organization – in the pandemic’s early days.   

They also illustrate why traditional public health measures such as better housing, less crowding, and improved ventilation may deserve more attention in modern TB control – strategies that have perhaps been too often sidelined to the shadows by modern drug therapies.

Despite the comparisons, the research team at the University of Cape Town has been studying the aerosol transmission of TB long before COVID appeared on the horizon, asserted the study’s lead author, Ryan Dinkele, in a press briefing on Tuesday morning.  

They did so with the help of a device developed by Robin Wood, another University of Cape Town researcher and study co-author, which can more sensitively detect the bacteria in aerosols emitted by a TB-infected person’s breath or cough.

“We have been working on this technique for a long period of time,” Dinkele said. “We did chat about whether we should implement our system for COVID. COVID came across our lines during this process.”

Conference sheds light on a neglected disease 

Tereza Kaseva, director of the WHO Global TB Programme

The three-day conference on lung health, attended by several thousand specialists and policymakers from around the world also casts its net on a wider array of respiratory diseases  – including pneumonia, asthma, chronic obstructive pulmonary disease (COPD) – and COVID-19.  Sessions also will address the two biggest environmental risk factors for lung health – tobacco smoke and air pollution.

However, most of the conference’s attention is focused on TB, which paradoxically remains one of the deadliest diseases on the planet, despite the fact that it is also one of the oldest.  And the COVID pandemic has only made that worse – dramatically reducing the number of TB-infected people who are being diagnosed and treated in 2020 – according to the latest Global TB Report, released by WHO just last week. 

“TB remains critically underfunded,” said Tereza Kaseva, director of the WHO Global TB Programme. “Global spending on TB is $5.3 billion, less than half of the $13 billion annually that we need,” she stressed, saying that the world urgently needs to invest in new TB diagnostics, treatments, and ultimately, vaccines.     

Additionally, TB is a “social disease” whose transmission is facilitated by poverty and marginalization, making it a disease endemic to many migrant groups and informal communities, she and others emphasized.  

Co-morbidities of TB & COVID are unexplored

Uvistra Naidoo, South African pediatric doctor and TB/COVID survivor

“TB is grossly underfunded, and that is why we are behind in the race,” said Uvistra Naidoo, a pediatric doctor and himself both a TB and COVID survivor. Not only governments are to blame, however, he added: 

“When I compare with HIV or cancer,” he added, “there is a lot more activism that happens on behalf of the patient in the latter.”

The COVID pandemic has only added fuel to the fire in another way – not only shifting resources but also saddling many former TB patients, like himself, with additional COVID disease risks.

Those co-morbidities are still poorly understood, said Naidoo who knows this from bitter first hand experience.

After beating drug resistant TB in a difficult three-year battle –  he came down with COVID in 2020, and continues to battle the effects of long COVID today.

“I picked up severe COVID-19 twice,” he said, speaking at The Union session with the aid of a nasal oxygen cannula.

“I’ve got complications to my heart, my lungs, and my adrenal glands recently. We’ve just found out and as you can see, I’m still intermittently oxygen dependent,” said Naidoo. He described how COVID, when it struck South Africa, infected almost everyone in his family  – as well as many in his professional community.

“I’ve lost a father, I’ve lost 25 medical colleagues, doctors and nurses. I’m beyond humbled. I think the courageous thing that we can show the general public out there is that to actually just describe with the TB front and the COVID-19 front, that we don’t know what we’re doing just yet.” 

Image Credits: Roche , The Union .

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