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Study on spread of COVID-19 in air conditioned bus

The coronavirus could be transmitted over a longer distance than previously thought, especially within an enclosed air conditioned environment, according to a study by a team of Chinese government epidemiologists.

The research by the Hunan-based team throws into question the official guidelines from China’s health authorities on COVID-19 prevention to keep “a safe distance” of 1-2m apart in public spaces. The new study indicates that the coronavirus can travel almost 5m, stay in the air for at least 30 minutes, and last for days on some surfaces.

According to the South China Morning Post, the findings were taken from the scientists’ study of a COVID-19 case subject who took a long-distance 48-seater bus ride and was later found to have infected 13 people in total.

The team observed via surveillance footage that the subject did not interact with fellow bus commuters throughout the ride, yet ended up infecting people who were seated about 5m away – or six rows apart. One of the passengers who was infected during the trip had boarded the bus after the subject and other infected passengers had already exited the vehicle. The researchers have linked this to airborne infection, possibly due to the latter patient’s inhalation of tiny particles exhaled by the first group.

The findings also blame the longer-than-anticipated infection distance on the enclosed air conditioned space.

“It can be confirmed that in a closed environment with air conditioning, the transmission distance of the new coronavirus will exceed the commonly recognised safe distance,” the researchers note, in a paper they co-authored for the peer-reviewed Chinese journal Practical Preventive Medicine.

“The possible reason is that in a completely enclosed space, the airflow is mainly driven by the hot air generated by the air conditioning. The rise of the hot air can transport the virus-laden droplets to a greater distance,” said the paper.

The Hunan-based researchers found the virus, depending on environmental conditions, could last for days on a surface where respiratory drops land. At around 37℃, they say it can last 2-3 days on fabric, glass, metal, plastic or paper. In addition, they found the virus could survive more than five days in human faeces or bodily fluids.  

To avert possible infections, the researchers advocate the wearing of masks and improving sanitation on public transportation. The former position is based on their findings that none of the patients who wore face masks on the bus became infected.

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