A growing collection of research suggests that COVID-19 spreads in the air indoors throughout enclosed spaces. A new study from the University of Georgia supports this theory, tracing a community COVID-19 outbreak back to an infected individual who was riding on a bus.
The research was focused on a COVID-19 patient in China, who likely spread the virus to fellow bus riders through the bus’s air conditioning system.
Study lead author Ye Shen is an associate professor of epidemiology and biostatistics at UGA’s College of Public Health.
“The possibility of airborne transmission has long been suspected, but with limited empirical evidence,” said Shen. “Our study provided epidemiologic evidence of transmission over long distances, which was likely airborne.”
“It was largely believed that close contact through droplets is a major route of transmission for COVID-19. However, the widely adopted social distancing and hand washing did not effectively prevent the transmission globally. Instead, the number of new COVID-19 cases increased steadily.”
In collaboration with epidemiologists at the Centers for Disease Control and Prevention in China, the researchers tracked COVID-19 infections following a large outdoor worship event in Zhejiang province. Some of the attendees traveled to the event in two buses.
Study co-author Professor Changwei Li explained that both buses had the windows closed and the air conditioning running,
but one bus carried a patient infected with the virus, while the other did not. The majority of the individuals that became ill rode on the same bus as the source patient.
Even though the two groups mixed in with a larger crowd at the worship event, the number of new cases traced to to the event were much lower, suggesting that the bus was the major point of transmission.
Furthermore, the experts found that some of the bus riders who later showed symptoms of COVID-19 were not sitting close to the infected passenger.
The study results show that COVID-19 can be spread through fine aerosol particles that are being circulated throughout enclosed spaces. The researchers hope that as the weather turns colder, their findings will persuade more people to wear face masks in public areas, especially in indoor spaces.
“Understanding the transmission routes of COVID-19 is critical to contain the pandemic, so that effective prevention strategies can be developed targeting all potential transmission routes,” said Shen. “Our findings provide solid support for wearing face covering in enclosed environments with poor ventilation.”
The study is published in the journal JAMA Internal Medicine.