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Volume 26, Number 11—November 2020

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

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To the Editor: In the research letter by J. Lu et al. (1), the authors claim that “The air outlet and the return air inlet for the central air conditioner were located above table C (Figure, panel B).” This sentence does not describe the actual layout depicted in the Figure, in which the air conditioner is located by table C and the exhaust fan is between tables B and D.

Furthermore, the authors do not provide evidence of why “Virus transmission in this outbreak cannot be explained by droplet transmission alone.” Their discussion does not mention the possibility that persons move around and may have been infected by touching surfaces, going to the restroom at the same time, or engaging in other close contact.

It is hard to understand how the authors conclude that “… strong airflow from the air conditioner could have propagated droplets from table C to table A, then to table B, and then back to table C.” According to the figure, air flows from table C to the exhaust fan (tables B–D). The authors do not provide evidence that the exhaust fan was not working; they ignored its presence. A simple measurement of air flow would answer this question.

The fact that “… none of the staff or other diners in restaurant X were infected” is another indication that the air conditioner was probably working. Also puzzling is the authors’ conclusion that “… the smear samples from the air conditioner were all nucleotide negative. This finding is less consistent with aerosol transmission.”

The authors’ conclusion that “… in this outbreak, droplet transmission was prompted by air-conditioned ventilation” is not supported by the data provided. They further conclude that “The key factor for infection was the direction of the airflow” but do not follow the airflow to the exhaust fan.


Ana M. RuleComments to Author 
Author affiliation: Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA



  1. Lu  J, Gu  J, Li  K, Xu  C, Su  W, Lai  Z, et al. COVID-19 outbreak associated with air conditioning in restaurant, Guangzhou, China, 2020. Emerg Infect Dis. 2020;26:162831. DOIPubMedGoogle Scholar


Cite This Article

DOI: 10.3201/eid2611.202948

Original Publication Date: September 11, 2020

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Table of Contents – Volume 26, Number 11—November 2020

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Please use the form below to submit correspondence to the authors or contact them at the following address:

Ana M. Rule, Johns Hopkins Bloomberg School of Public Health Department of Environmental Health and Engineering, 615 N. Wolfe St. E6614, Baltimore, MD 21205; USA

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Page created: September 08, 2020
Page updated: October 19, 2020
Page reviewed: October 19, 2020
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.