Not giving a monkey’s about how infectious diseases are transmitted

We are currently being a bit distracted from the latest wave of COVID-19 infections, by the latest new disease to hit the headlines: monkeypox. A bit grim but that is where we are. The two infectious diseases are very different. The number of cases of monkeypox is tiny, in comparison with COVID-19, and many of the cases are found in men who have sex with men.

Epidemiologists can model how this spread works, in the following sense: If you assume prolonged close contact comes with a very large risk, but casual social contact has a much much lower risk. Then monkeypox can spread through a network of contacts of sexual partners – even though monkeypox is not a sexually transmitted disease – but show much less transmission in the general population.

So if we assume that transmission is much higher for contact, or very close contact, for monkeypox, but can occur across a room for COVID-19, then we can explain the different patterns of transmission of COVID-19 and monkeypox. But I don’t think we understand why these very different rules of transmission apply. Maybe monkeypox has a different route into the body than COVID-19 – COVID-19 likely is mostly inhaled? Or maybe not.

The monkeypox virus is a bigger virus than SARS-CoV-2 (the virus that causes COVID-19), see image* above. But as SARS-CoV-2 likely spreads in droplets a lot larger than the virus, this seems unlikely to be important. But of course it could be, we don’t have the data here. The monkeypox virus has a protein shell (in blue above) which SARS-CoV-2 does not. Naively this would make the monkeypox virus tougher and so able to hang around in the environment or air longer than SARS-CoV-2, but SARS-CoV-2 is the one that seems to be frequently transmitted across a room.

We need more data to work out why these two viruses have such different transmission patterns. Unfortunately, I am not sure the work to gather this data will be done. It would be expensive to do, and I am not sure where the money would come from. Take, for example, The Wellcome Trust, which is one the world’s biggest funders of medical research. Its page on infectious diseases is heavily focussed on vaccines. Vaccines are wonderful, and it is great to see funding for them. But they are clearly not enough on their own, to stop repeated waves of COVID-19 infection. And the webpage is illustrated by a picture of people washing their hands outdoors. I am not aware of any good data suggesting washing hands reduces the risk of COVID-19 transmission, but there are plenty of good studies showing transmission indoors. I suspect that the authors of the webpage knows a lot more about vaccination than about the mechanisms of transmission of infectious diseases. And they control the funding.

* Image is from PDB. Thanks to them.

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