Speaker Topic:

"Dilution for avoiding SARS-CoV-2 transmission"

The COVID-19 pandemic has generated new data and knowledge for understanding the transmission respiratory infection in air. I shall argue that the transmission of SARS-CoV-2 has been predominated by the inhalation route, although the roles of short- and long-range inhalation may differ for the Omicron variant and those earlier ones. The most important transmission phenomenon is the less or rare occurrence of outdoor transmission, and most observed outbreaks with measured ventilation rates occurred in spaces without sufficient dilution. Effective dilution can be achieved by ventilation, filtration, airborne pathogen deactivation, and/or spaciousness. It appears that the dilution requirement for avoid Omicron transmission is much higher than that for early variants. mass wearing of surgical masks seems to be effective with most of indoor spaces for early variants of SARS-CoV-2, while insufficient for Omicron variant. There is a need for studying transmission of air-related diseases and associated air hygiene, just as we did for water-related diseases and associated water hygiene.

Speaker Biography:

Yuguo Li is a Chair Professor of Building Environment at HKU. His current research topics include city climate, environment studies of infection and indoor environment. He serves as Editor-in-Chief of Indoor Air. Since early 2020, he has collaborated with WHO, Guangdong CDC, Hunan CDC, Jiangsu CDC, and Hong Kong EPD and studied the transmission routes of SARS-CoV-2 in buildings. He is a member of the WHO IPC GDG and WHO Environment and Engineering Control Expert Advisory Panel (ECAP) for COVID-19.