One of the studies that convinces many (including me) that COVID-19 is mostly transmitted directly across the air, is a “superspreader” event in a restaurant in Guangzhou, China. It looks like a single infected person infected five people at other tables, in addition to four people on the same table as them. The restaurant was very badly ventilated, but there was a system that just circulated air around the table the infected person sat at, and the other two tables where people become infected. This is all perfectly consistent with the infected person breathing out virus that is then carried by air currents across the restaurant, and breathed in by people at another table. However, we can’t rule out alternative mechanisms, for example what is called the fomite route.
The fomite route is via surfaces and our hands, and is why we are asked to wash our hands and why restaurants, supermarkets have sanitiser gel etc. A paper by Zhang and coworkers went back to CCTV data recorded of the restaurant, and asked a couple of questions, one of which is basically: If transmission is via fomite, then we would expect to find that the people who handled surfaces and objects the most, and then touched their lips, were the ones that became infected. Essentially, members of the resaerch team sat through lots of CCTV footage and counted how many times a person touched a plate, the table, etc and also (to look for transfer to their respiratory tract) at how often they touched their lips.
And the result is that the people who touched surfaces touched by the infected person the most, were not the ones who became infected. So there is no evidence to support fomite transmission. No evidence to say that washing your hands, using sanitiser gel, wiping down surfaces, etc will make you safer. Now, the study is more the start than the end of research on transmission of COVID-19 via hands and surfaces*. But as there is no evidence that I know of that supports the fomite route for COVID-19, and we now have at least some (relatively weak) evidence against it, then it is surprising how much hand sanitiser we are going through.
* There is very very little work out there, so it is great to see this study but it does have limitations. In particular, I think it assumes that the fomite route is that the virus starts on the hands of an infected person, is transferred to an object or surface, and then picked up on the hands of another person who can then become infected. I would guess that more likely would be the virus being breathed out, landing on a surface, and then being picked up from that surface.
Chance & Necessity 