http://dx.doi.org/10.13140/RG.2.2.36685.38881
[dude from Reddit found good parts to read]
Among passengers who eventually developed COVID-19 on Bus #2, three were asymptomatic, three had mild symptoms, and the remaining seventeen cases had moderate symptoms. The severity of secondary cases was not associated with their proximity to the index patient on the bus (correlation, 0.00; P=0.99).
Our data strongly suggest that airborne transmission contributed to the COVID-19 outbreak among lay Buddhists in Zhejiang province. The index patient was the only person exposed to individuals from Wuhan and the first at the event to be diagnosed with COVID-19 suggesting a high probability that she was the source of the outbreak. The two buses mimicked a quasi- experiment and the second unexposed bus, which left and arrived at the temple at similar times with similar individuals, provided a credible control group. Both buses had an air conditioning system on a re-circulating mode, which may have facilitated the spread of the virus in the exposed bus. Attack rates on the exposed and unexposed buses were sharply distinct (34.3% versus 0%) suggesting that the exposure and the environment in which the exposure took place contributed to this outbreak. Additionally, passengers sitting closer to the index case on the exposed bus did not have statistically higher risks of COVID-19 as those sitting further away. If COVID-19 transmission occurred solely through close contact or respiratory droplets during this outbreak, risk of COVID-19 would likely be related to distance from the index case and ‘high-risk’ zones on the bus would have more infected cases. Our findings suggesting airborne transmission of COVID-19 is in line with a past report of a SARS outbreak on a plane.
It should be noted that, except for a passenger sitting next to the index, all passengers sitting close to a window on the left side of the bus remained healthy. This may be related to airflow within the bus; however, we were unable to empirically test this hypothesis. Similarly, transmission at the worship event between the bus rides only led to few infections, and all of those reported close contact with the index case. These data suggest that forced, circulating air might play an important role in airborne spread of the virus.
She [patient 0 on the bus] was initially asymptomatic during the bus trip but started to have cough, chills, and myalgias on the evening after returning from the temple.
Among the trainees, only the index patient traveled from Wuhan. She reported no fever during the training, however, her colleagues observed her taking unknown medications throughout the workshop. The index patient returned to Wuhan on January 15. She developed a fever (38°C) and cough on January 17 and was diagnosed with COVID-19. Between January 16–22, a total of 15 trainees who attended the workshop, including the index patient, were diagnosed with COVID-19. The attack rate was 48.3% (95% CI, 31.4– 65.6).