Explained: What a study from China tells us about airborne transmission in public transport

A new study published in the journal JAMA Network suggests airborne transmission in a bus in China led to one infected individual spreading of COVID-19 to 23 other fellow passengers. Analysing community transmission in China’s Zhejiang province, the study reports that 128 individuals took two buses on January 19, 2020 — 60 in bus 1 and 68 in bus 2 — on a 100 minute round trip to attend a 150-minute worship event. The source patient was a passenger on bus 2 and both the buses had central air conditioners functioning in indoor recirculation mode. Among these 128 individuals, 15 were men, 113 were women with a mean age of 58.6 years. On bus 2, 24 individuals turned out to be positive after the event, while none of the individuals in bus 1 were affected. Seven others who turned positive after the outdoor event had all come close to the index patient.