Thread by @GidMK

1/13 There are still tons of news pieces every day about whether #COVID19 is 'airborne'

This is understandable, because airborne=infectious=scary

But we know that the disease isn't airborne, at least not in the traditional sense

What's going on?

2/13 The idea with airborne diseases is that they are far more infectious than non-airborne ones because people often catch the disease with only minimal or even no direct contact with infected people

3/13 There have been cases of measles demonstrating that a level of virus high enough to be infectious can stay in a room up to ~75 minutes after the person who is sick has left

4/13 And we know, from every investigation so far, that COVID-19 simply isn't infectious enough for this to be the MAIN route of infection

Measles, for example, is roughly 6x as infectious as COVID-19. Mumps is 4x

5/13 It's most likely that MOST COVID-19 infections are caused by close-range droplets - a sick person coughs or sneezes (or talks) and contaminates you or a surface which you then touch (called "fomites")

6/13 All of this has been known for some time, and is where, for example, the 1.5-2 metre spacing rules come from

7/13 Does this make the question about airborne spread entirely obsolete?

Not quite

There's still the pesky outliers to deal with

8/13 As I said, MOST infections are clearly not airborne

But, we've also seen evidence that there is probably SOME level of airborne transmission - rare, perhaps, but it may happen

For the sake of argument, let's say it's 1% of infections

9/13 Think about it - if everyone's social distancing properly then MOST infections - all of the short-range ones - will be prevented

We've seen this happen all over the world

But the 1% may not be reduced nearly as much by these measures

10/13 Thing is, that last 1% is also the hardest to get at. It requires even further investments - not just universal masking, but revising aircon, making long-lasting changes to office structures etc

It's quite hard to prevent us breathing the same air

11/13 And we don't NEED to prevent these infections (we might WANT to)

To stop the epidemic, the key is to reduce Reff below 1, and we have seen that this is eminently possible using social distancing, testing, contact tracing, and other measures

12/13 The marginal benefit to eliminating the possibility of ANY airborne spread is small, but the cost is big

Which is why even though there may be the occasional airborne case, it's not a huge issue for most governments and agencies

13/13 So yes, there may be SOME cases caused by viral particles in the air

We may eventually have definitive evidence that it is possible and has happened

But it remains unlikely that it has or will play a significant role in the pandemic