An analysis of three Covid-19 outbreaks: How they happened and how they can be avoided
By Javier Salas and Mariano Zafra
A crowded restaurant to celebrate the Chinese New Year; 100 workers infected inside a 19-story building; a group of devout Buddhists travelling by bus for a religious ceremony. These were the scenarios for three outbreaks of Covid-19 that have been carefully documented by the authorities. What happened in each one? What were the risk factors? What lessons can be learned, now that we are trying to get back to normal and return to restaurants, offices and other shared spaces?
The office
In a single wing of a call center in Seoul, in South Korea, the risk of infection was multiplied by four key factors: close, prolonged contact between numerous people, in an enclosed space.
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The restaurant
A New Year’s meal in the Chinese city of Guangzhou on January 24 provides the best example of how to reduce indoor risks. This scenario has been analyzed in detail in two different studies (1, 2) by the Chinese health authorities, who concluded that poor ventilation can be a decisive risk factor if contact is maintained during prolonged periods. Again, time plus social proximity multiplies the risks.
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The bus
Chinese authorities and researchers from US universities are analyzing an outbreak at a Buddhist ceremony that was attended by people travelling on two buses for a total of 100 minutes – 50 minutes each way. A woman with symptoms was traveling on one of the vehicles, where the air was recirculated; 23 passengers were infected. “Patient 0 in this outbreak appears to have been a superspreader,” explains Emily Gurley, an epidemiologist at Johns Hopkins University. As at the restaurant, transmission could be explained by aerosols and droplets traveling longer distances due to the draft from the window or the air conditioning,” she adds.
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