Evolution of Understanding of COVID-19 Transmission

In early 2020, a respiratory virus swept across the world. The World Health Organization (WHO) confirmed pandemic status and the virus was identified as a coronavirus with superlative transmission properties. Using work from the 1950s, the WHO declared that the virus was transmitted through respiratory ‘droplets’, which were expelled by infected persons through coughing/sneezing. These would fall to the ground within 1–2 m. Scientists investigating viral transmission questioned this premise because recent work had shown that viruses populate the smallest respiratory particles, remaining airborne for much longer than larger ‘droplets’ and capable of spreading throughout the indoor environment. Advice such as handwashing, surface disinfection and social distancing was not as important as face masks and adequate indoor ventilation. People needed to know that poor ventilation constituted the highest risk for contracting the virus. Instead, homes and surfaces were disinfected and social distancing was maintained in community settings. The scientists formed a consortium named Group 36 in order to contest the WHO over airborne transmission but they could not present definitive evidence in the short term to reverse initial guidance. This account details the evolution of understanding of COVID-19 transmission and the role of Group 36 and others in challenging WHO-based policies based on dated physical science.