American and Chinese researchers have found that 23 people riding a bus caught coronavirus after a previously-diagnosed asymptomatic passenger, regardless of other passengers' proximity to the individual, spread the virus via the bus's ventilation system.
According to the unpublished study, bus air conditioning systems may accelerate the spread of coronavirus by circulating air within confined spaces, with the research also noting that masks may also be ineffective on buses.
The researchers drew their conclusions after examining a case in which 23 out of 67 passengers on a trip were diagnosed with coronavirus via an asymptomatic passenger, through the bus's centralized ventilation system, whereas the later use of that same bus without an asymptomatic passenger did not result in cases of infection.
Researchers estimate that passengers sitting close to the asymptomatic passenger were not more prone to infection than those sitting far away. This led to the conclusion that the air conditioning system and the enclosed environment helped spread the virus.