Professor Ooi Eng Eong, the deputy director of Duke-NUS’ emerging infectious disease programme, speaking at a Straits Times webinar on Covid-19, said that it is unlikely that Covid-19 can be spread through air-conditioning even if the virus is airborne.
He added that if an infected person coughs or expels the coronavirus and it gets sucked into the building’s air-con system, there wouldn’t be enough particles for it to spread through the air vent because “the entire process would have diluted the virus so much that whoever manages to inhale it would not have enough particles to cause the infection (in their system)”.
Citing a study released in preprint on July 22, Professor Dale Fisheer, a senior infectious diseases expert at the National University Hospital, said that although airborne coronaviruses may be infectious, the viral load found in the droplets were small and not enough to cause disease.
Compared to other infectious diseasus like measles (for example), Covid-19 has an R0 (pronounced R-nought, which we will explain shortly) of 2.5.
Now, R0 refers to the transmissibility of a virus. and R0 of 1 means each infected person will spread the disease to one other person, who will in turn spread it to one other person.
In the case of Covid-19, with an R0 of 2.5, it means that 1 infected person will spread the diseas to 2.5 other people, who will then each spread their disease to 2.5 more people, so on and so forth.
Prof Ooi added that for an infection to occurt, a “minimum number of viruses would have to get into the body.”
However he added, reducing the risk of transmission still relies heavily on measures such as wearing masks, safe distancing and good personal hygiene.