A study of an air-conditioned restaurant in Guangzhou, China, found coronavirus spread to three separate families eating in the restaurant ― all of them sitting in proximity of the air conditioning unit.
The direction of airflow seemed to correlate with the diners who contracted the virus, researchers said. Among the 83 customers who ate in the restaurant on the same floor as the infected person that day, 10 became ill with coronavirus. The other 73 were identified as close contacts and quarantined for 14 days.
The most likely cause of the outbreak was droplet transmission, researchers said. But larger respiratory droplets remain in the air for only a short time and travel short distances, generally less than 3 feet, they added. The distances between those already infected and people at other tables, who went on to contract the virus, were greater than 3 feet.
“Strong airflow from the air conditioner could have propagated droplets” between the tables, researchers suggested.
Hunter said the Chinese study is consistent with the “droplet spread” hypothesis and “does not, in any way, imply [Covid-19] is spread by air conditioning.” He also cites the case of the Diamond Princess cruise ship. It was suggested that air conditioning onboard the ship, where some 700 people were infected, spread the virus, but the evidence does not back this up.
One study awaiting peer review suggests most transmission appears to have occurred through close contact and infected surfaces and objects. Hunter agreed, adding that case reports show none of those who were infected appeared to have picked up the virus while quarantined in their rooms.
However, Professor Qingyan Chen, an expert in mechanical engineering at Purdue University, Indiana, believes air conditioning could potentially spread COVID-19, as the units aren’t designed to filter out particles as small as the coronavirus.
“The coronavirus could be airborne so the virus could be spread through air conditioning systems, although the virus concentration in air is very low,” he told HuffPost UK in an email.
If you visit a grocery store (or travel on a bus or a train) for a few minutes up to a few hours, the risk of being infected through airborne virus is low, he said. However, if you’re exposed to air with a very low virus concentration for a long time ― such as in an office ― it is “likely to be infected.”
While more research is needed, virologist Julian Tang from the University of Leicester said we should assume airborne transmission is possible unless experimental evidence rules it out ― not the other way around ― and that people should take precautions to protect themselves, he told the journal Nature.
Those precautions are particularly wise in crowded, indoor environments. Hunter said facilities managers should be turning down the volume of airflow in buildings with air conditioning to prevent droplets from spreading further.
Other studies have recommended increasing ventilation, not recirculating air and reducing the numbers of people in indoor environments to limit the spread.
Where ventilation is inadequate and density of people is high, some experts recommend the use of masks and respirators.
source: huffpost UK