The SARS-CoV-2 Transmission Riddle - Part 2

We need clarity in the evidentiary rules about how viruses spread (Revised January 2024)

This is the second of a re-run of our Transmission Riddle series, which was originally posted in 2022. Each post has been updated and reworked with what new evidence we could find. The serial numbers of the original posts may not correspond as we expand, merge, edit and add, like a concertina. 

In late 2020, the World Health Organisation asked us to review and summarise the evidence of what was known about the transmission mode of SARs-CoV-2. How pathogens are transmitted from person to person - directly or indirectly - is central to managing this or any other epidemic.  

For example, in Lecture 2 of the John Snow course, we discussed how Snow tried to ascertain the timings and evolution, the circumstances and the outcomes of each outbreak. In Lecture 14, we reported how he used a logical process called induction to discover the association between water and cholera and then went one step further. He described several cases of transmission from contact, especially whenever people came i…