Air Conditioning May Spread Coronavirus — 9 People Were Infected at a Restaurant

The study, while small, points to safety problems once restaurants reopen

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When restaurants are able to reopen, they may need to do more than just move their tables further apart. A new study found that nine people were infected with the new coronavirus, COVID-19, after they dined at a restaurant near a person who had not yet shown symptoms, likely because the air conditioning system recycled virus particles through the room.

The study, though small, indicates that it will be tougher for restaurants, who are already suffering, to safely reopen.

According to the study, which will be published in Emerging Infectious Diseases, a journal from the Centers for Disease Control, the infected diner was eating at a restaurant in Guangzhou, China, in January with nine other people. Their table, and two others, were directly in line with the restaurant’s air conditioning unit. Four people at the infected diner’s table later tested positive for COVID-19, along with five people at the neighboring tables.

The researchers wrote that the virus typically transmits via large respiratory droplets between people within short distances of each other, but “virus transmission in this outbreak cannot be explained by droplet transmission alone,” they wrote. “However, 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.”

Encouragingly, though, the virus did not spread far — the 73 other people who dined in the five-story restaurant that day and the eight employees working on the floor with the infected cases were all told to quarantine for 14 days, and none tested positive for COVID-19. That includes the people dining at nearby tables that were not directly in line with the air conditioner.

“To prevent the spread of the virus in restaurants, we recommend increasing the distance between tables and improving ventilation,” the researchers suggested.

The study, though, “has limitations,” they wrote. It was a small sample size, and they did not replicate the virus transmission in a lab or have a control study to compare it to. Still, the researchers said the data was sufficient to show that the air conditioning was the cause of virus transmission.

“We conclude that in this outbreak, droplet transmission was prompted by air-conditioned ventilation,” the authors wrote. “The key factor for infection was the direction of the airflow.”

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And the research points to potential hazards in reopening restaurants, businesses and offices, experts said.

Dr. Harvey V. Fineberg, the head of the Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats at the National Academies of Sciences, Engineering and Medicine, told The New York Times that the study was “provocative and eye-opening.”

“It’s illuminating for the kind of thing we need to keep learning about as we try to configure safe work spaces,” he said. “Not just safe restaurant and entertainment venues but where you go to work.”

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