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Tuesday, December 7, 2021

Tuberculosis, like Covid, spreads in aerosols, scientists say

Developing centuries of medical dogma, a group of South African researchers found that breathing may contribute more to the spread of tuberculosis than coughing, a common symptom.

Researchers estimate that up to 90 percent of the tuberculosis bacteria excreted by an infected person can be carried by tiny droplets called aerosols, which are released when the person exhales deeply. The results were presented on Tuesday at an online conference.

The report reiterates an important finding about the Covid pandemic: The coronavirus also spreads in aerosols that are carried in the air, especially indoors – a transmission route that has been underestimated as the pandemic began to unfold.

Tuberculosis is caused by the bacteria Mycobacterium tuberculosis, which usually affects the lungs. It is the world’s deadliest infectious disease since Covid-19, claiming more than 1.5 million lives last year – the first increase in a decade, according to a report released last week by the World Health Organization.

As the Covid pandemic disrupted access to healthcare and supply chains around the world, 5.8 million people were diagnosed with TB in 2020. But the WHO estimates that about 10 million people have been infected. Many may unwittingly spread the disease to others.

“Our model suggests that in fact aerosol production and tuberculosis can occur independently of symptoms,” said Ryan Dinkele, a PhD student at the University of Cape Town who presented the results.

The discovery helps explain why cramped, enclosed spaces such as prisons are often breeding grounds for tuberculosis, like Covid. And research shows that some of the methods used to limit the transmission of coronavirus – masks, open windows or doors, and being outdoors as much as possible – are important in the fight against tuberculosis.

“Those of us who do TB look at Covid and say, ‘Wow, this is just an accelerated version of TB,’ said Dr. Robert Horsburg, an epidemiologist at Boston University who was not involved in the work.

Previously, researchers believed that most TB transmission occurs when an infected person coughs while spraying droplets containing the bacteria onto others. It was believed that some bacteria are secreted by breathing, but much less than by coughing.

The new discovery does not change this understanding: one cough can expel more bacteria than one breath. But if an infected person breathes 22,000 times a day, coughing up to 500 times, then coughing accounts for only 7 percent of the total bacteria shed by an infected patient, Mr Dinkele said.

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On a crowded bus, at school or at work, where people sit for hours in a confined space, “just breathing will bring more infectious aerosols than a cough,” said Mr Dinkele.

In so-called tidal breathing, tiny air sacs in the lungs open when you inhale, and then when you exhale, bacteria are carried from the lungs through aerosols. Due to their smaller size, aerosols released during tidal breathing can remain in the air longer and travel further than droplets released during coughing.

As with Covid, some TB patients transmit the disease to many people and may shed a lot of bacteria, while others infect few people around them. But even if 90 percent of the bacteria expelled by an infected person were aerosolized, this route of transmission would not necessarily account for 90 percent of new cases, warns Dr. Sylvia S. Chiang, who studies the disease at Brown University.

However, the finding suggests that doctors should not wait for TB patients to arrive at clinics with severe coughing and weight loss, which are common symptoms, experts say.

“We just need to screen the entire population, just like you, if you’re looking for a lot of Covid,” said Dr. Horsburg.

The discovery was largely due to technology developed by Dr. Robin Wood, Distinguished Professor of Medicine at the University of Cape Town in South Africa. The device can collect aerosols from infected people and detect bacteria in them.

The diagnosis and treatment of tuberculosis has changed very little over the decades. “It’s time to start using today’s cutting-edge technology to treat an old disease,” said Dr. Wood. He added that with some tweaks, the system could also be used to study other diseases, including Covid.

Tuberculosis has been around for millennia, and its cause has been known for almost 150 years.

“And yet we are still learning something new about such a fundamental part of his biology,” said Mr Dinkele. “It is humiliating to know that we need to be so careful when it comes to dogmatic approach in the field.”

World Nation News Deskhttps://www.worldnationnews.com
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