AC air flow spread Covid-19 in China restaurant

On January 24, nine people from three families contracted COVID-19 while having lunch at a restaurant in Guangzhou, China. Another 81 who were within the eatery didn't.

The infections, consistent with an analysis by Center for Disease Control (CDC) experts in China, happened because the three families were within the draught of the identical air conditioning as the index patient, although they were on different tables.

The findings now offer new insights how the virus travels (it infected only those within the atmospheric condition while others were safe); the challenge in detecting infected persons (the index patient failed to have any symptoms); and consequences for closed, air-conditioned spaces (restaurants, offices, even public transport) because the world struggles to see how people can return to everyday routines.

On January 23, family A travelled from Wuhan and arrived in Guangzhou. On January 24, the index case-patient (patient A1) ate lunch with 3 other members of the family (A2–A4) at restaurant X. Two other families, B and C, sat at neighbouring tables. Later that day, patient A1 experienced fever and cough and visited the hospital. By February 5, a total of nine others (four members of family A, three members of family B, and two members of family C) had become ill with COVID-19, said the research letter published went to journal Emerging Infectious Diseases.

The researchers say the infections show the virus was spread through droplets carried within the air-conditioning draught.

The lack of infection in others at two tables reachable (but not within the line of the airflow), and in other floors of the restaurant seemed to suggest the virus didn't spread through "aerosol transmission".

If an epidemic spreads as an aerosol, it's harder to contain since it lingers within the air for longer and disperses more efficiently over long distances.