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COVID-19 Outbreak Associated with Air Conditioning in Restaurant, Guangzhou, China, 2020

Our take —

As many countries around the world move into the warmer season and begin using air conditioners more frequently, this study provides evidence that better understanding of air flow patterns may help mitigate transmission risk. This may be particularly important to consider as restaurants and other public spaces reopen and integrate social distancing practices into their operations.

Study design

Case Series

Study population and setting

Between January 26 and February 10th, 2020, an outbreak of SARS-CoV-2 was observed among 3 family clusters in Guangzhou, China. All three families, making up a total of 10 individuals, had eaten at the same air-conditioned restaurant during the period and had sat at adjacent tables. The restaurant where these families had eaten was air-conditioned, did not have windows, and the distance between each table in the dining area was about 1 meter. The authors conducted an investigation of these ten individuals, along with testing of the other individuals in the restaurant and smear samples from the air conditioner.

Summary of Main Findings

All three families ate lunch at the same restaurant on January 24th. The index patient, one of the members of the families who had traveled to Guangzhou from Wuhan, went to the hospital later that same day with symptoms of SARS-CoV-2. By February 5th, a total of nine others had tested positive for SARS-CoV-2. The only known exposure for these individuals was the index patient at the restaurant, and they each spent between 50 and 70 minutes of overlapping time at the restaurant with the index patient. The authors hypothesize that transmission of the virus cannot be explained by droplet transmission alone, given that respiratory droplets usually travel less than 1 meter, but instead may be explained by the strong airflow from the air conditioner. This hypothesis may explain why these families were infected (given where they were seated relative to the airflow) and why staff members and others were not. No virus was detected on the smear samples from the air conditioner inlet or outlet.

Study Strengths

The hypothesis that transmission may be exacerbated by the direction of airflow is supported by 1) the fact that others in the restaurant were not infected and 2) the positioning of the air conditioner with respect to the tables where the families who were infected were sitting.

Limitations

The authors did not simulate the airborne transmission route by experimentally examining aerosolization patterns at the restaurant.

Value added

This study provides a hypothesis of a transmission route (aerosolized droplets) that may be exacerbated by environmental conditions (direction of airflow from air conditioner).