The SARS-CoV-2 Transmission Riddle - Part 2

We need clarity in the evidentiary rules about how viruses spread

In late 2020, the World Health Organisation asked us to review and summarise the evidence of what was known on 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, only after discovering that cholera was a waterborne disease could the outbreak be contained by separating drinking water from wastewater. Understanding transmission is, therefore, essential to understanding when and how to intervene. 

We used systematic review methods to search for the most likely modes of transmission: airborne (a vague term including big droplets from sneezes to fine aerosol or even air), contact, fomites (dust particles), oro-faecal and vertical (mother to baby). 

Right at the outset, we were struck by the poor quality of many of the studies, the dire reporting that often led to missing details and studies that used a variety of methods - when reported - and the contrasting resul…