The debate over airborne COVID-19 transmission persists, but evidence is mounting. Beyond large droplets from coughing or sneezing, tiny aerosols suspended in air may drive spread. A peer-reviewed Chinese study details how one bus passenger infected nearly a third of riders.
Once dismissed by some authorities, airborne transmission is gaining traction among respiratory virus experts. Research has detected viral particles in micro-droplets lingering in the air, generated even by talking.
Experts from China's Centers for Disease Control and Prevention published findings in JAMA Internal Medicine on September 1, 2020. They investigated passengers on two buses heading to a religious event in Ningbo, Zhejiang Province, on January 19—a trip lasting about 50 minutes.
On bus number 2, a 60-year-old asymptomatic passenger, previously exposed in Wuhan, sat on the right side in a middle row. Shockingly, 23 of 68 passengers tested positive.
Infections extended far beyond seats near the index case—reaching front and rear rows. If limited to large droplets, spread would typically stay within 1-2 meters. With no cough from the asymptomatic source, researchers point to aerosols. The bus AC recirculated air without fresh intake, dispersing virus cabin-wide.
This occurred mid-January during Chinese New Year, pre-national lockdown, so no masks were worn. A similar March 2020 report described another bus case infecting 13 at distances of 2-4.5 meters.
