It’s in the air (somebody open a window)

One of the important side-discoveries of the pandemic is how wrong we have been on the airborne spread of infectious disease. For years, the consensus has identified the main threat as large droplets expelled over short distances in sudden bursts: “coughs and sneezes spread diseases”. This was in part a reaction against the errors of miasma theory, which once blamed “bad air” for cholera – until it turned out to be water-borne.

This was the logic behind social distancing for Covid: stand back a couple of metres and you can avoid large droplets spread over short distances by an infected friend coughing. It turns out, however, that fine aerosols of smaller droplets, carried simply on the breath, can travel further, hang in the air longer and are much more important as a factor in infectious spread.

Now there’s new evidence that our whole strategy for containing TB is also flawed by the same error.

Breathing is enough to spread the bacteria that causes tuberculosis, research presented at a major conference on Tuesday shows, potentially forcing the medical community to rethink decades of containment strategy focusing on coughing alone.

Using state-of-the-art equipment, at team at the University of Cape Town in South Africa measured the disease-causing Mycobacterium tuberculosis (Mtb) in 39 people with TB.

They looked at aerosols released during regular breathing, deep breathing and coughing and found that after five minutes all three produced particles containing the dangerous bacteria.

And while coughing produced three times more Mtb than breathing, the research notes that because people breathe all day long, simply exhaling may contribute more than 90 percent of airborne Mtb.

Time for us to rethink ventilation across all our infrastructure. Some countries have already started.