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A team of South African researchers has discovered that, subverting centuries-old medical dogma, breathing may be a greater contributor to the spread of tuberculosis than cough, the most important symptom.
Researchers estimate that as much as 90 percent of TB bacteria released from an infected person can be carried in tiny droplets called aerosols that are expelled when a person exhales deeply. The findings were presented at a conference Tuesday. scientific conference edited online.
The report reflects an important finding of the Covid pandemic: The coronavirus also spreads through the air, especially in aerosols carried in confined spaces. not widely appreciated when the pandemic begins to spread.
TB is caused by a bacterium called Mycobacterium tuberculosis, which usually attacks the lungs. Claims to be world’s deadliest infectious disease after Covid-19 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.
5.8 million people were diagnosed with TB in 2020 as the Covid pandemic has disrupted access to healthcare and supply chains worldwide. However, WHO He estimates that about 10 million people are infected. Many may be infecting others without realizing it.
“Our model suggests that aerosol formation and TB formation may occur independently of symptoms,” said Ryan Dinkele, a graduate student at the University of Cape Town, who presented the results.
The finding helps explain why tightly packed confined spaces such as prisons are breeding grounds for TB as well as for Covid. Research shows that some of the methods used to limit coronavirus transmission (masks, open windows or doors, and being outdoors as much as possible) are important in reducing TB.
Boston University epidemiologist Dr. “We tuberculosis people look at Covid and say, ‘Wow, this is just an accelerated version of tuberculosis,'” said Robert Horsburgh.
Researchers previously believed that most transmission of TB occurs when an infected person coughs and sprays droplets containing the bacteria onto others. Some bacteria were thought to be released when a person breathed, but much less so than when coughing.
The new finding doesn’t change that understanding: A single cough can expel more bacteria than a single breath. But if an infected person breathes 22,000 times a day and coughs up to 500 times a day, the cough makes up as little as 7 percent of the total bacteria spread by an infected patient, Dinkele said.
On a crowded bus where people sit indoors for hours, or at school or at work, “just breathing contributes more to infectious aerosols than coughing,” Dinkele said.
In so-called tidal breathing, inhalation opens small air sacs in the lungs, and then exhalation carries bacteria from the lungs via aerosols. Because of their smaller size, aerosols released by tidal respiration can stay in the air longer and travel farther than droplets emitted by coughing.
As with Covid, some TB patients spread the disease to many people – and can release a lot of bacteria – while others infect a few people around them. But even if 90 percent of the bacteria expelled by an infected person is carried in aerosols, Dr. Silvia S. Chiang warned that this mode of transmission will not be responsible for 90 percent of new cases.
Still, experts said the finding suggests that doctors shouldn’t expect tuberculosis patients to come to clinics with severe coughing and weight loss—no obvious symptoms.
Dr. “We need to screen the entire population, just like you would if you were looking for a lot of Covid,” Horsburgh said.
The discovery was largely due to Dr. It happened thanks to technology developed by Robin Wood. The device can collect aerosols from infected people and identify the bacteria inside.
The diagnosis and treatment of TB has changed little in decades. Dr. “It was time to start using modern, cutting-edge technology to approach an ancient disease,” Wood said. With some tweaks, the system could also be used to study other diseases, including Covid, he added.
TB has existed for thousands of years and its cause has been known for about 150 years.
“We’re still discovering new things about such a fundamental part of its biology,” said Mr Dinkele. “It’s humbling to realize that we have to be so careful when it comes to a dogmatic approach in a field.”
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