A team of Singapore-based scientists last week discovered that the Diamond Princess’s air conditioning systems may be what caused so many people living aboard to be infected with the COVID-19 virus. After collecting samples from three of the ship’s suites before and after cleaning, it was found that in the room that hadn’t been cleaned, 13 out of 15 sampled spots in the room tested positive for the virus – including air outlet fans and air conditioning units. The toilet, sink and door handles also tested positive for the novel coronavirus, which to date has infected almost a million and killed more than 46,000.
“There was extensive environmental contamination by one SARS-CoV-2 patient with mild upper respiratory tract involvement,” said the study, which was published in the Journal of the American Medical Association. “Swabs taken from the air exhaust outlets tested positive, suggesting that small virus-laden droplets may be displaced by airflows and deposited on equipment such as vents”.
The findings are backed by the recent announcement of a Chinese health official, who also suggested the virus may be capable of spreading via an airborne route. But the Chinese Center for Disease Control and Prevention countered the claim almost immediately, insisting that the novel coronavirus is not an airborne virus.
The scientists’ findings are novel and put the theory that the disease is not airborne into serious question. Until now, health experts have warned that the coronavirus is a respiratory virus which spreads mostly through droplets generated when an infected person coughs or sneezes, or through droplets of saliva or discharge from the nose. Given one single cough can produce up to 3,000 droplets, and a number of those particles can land on people or objects, it’s no wonder the virus is spreading as rapidly as it is. Communities have been told social distancing and extensive hygiene and sanitation measures, such as cleaning hands frequently with an alcohol-based hand rub or soap, are the best ways of staving off the virus. But what if air conditioning is also partly responsible for the spread of infection?
In Israel, where six Israelis have died from COVID-19 in just one day as cases surge past 6,000, citizens are urging the government to make a clear statement on whether the virus can be transmitted via air conditioning or air outlet fans. As the virus continues to spread at lightning speed, many are wondering whether the time is right to replace central air conditioning units, or even to switch them off for good until after the virus peaks. Interestingly, much of the health advice being released right now advises those in self-isolation to increase ventilation through opening windows and turning on air conditioning. Is such advice putting us at risk?
Theories with respect to transmission via air conditioning are mixed, and as of yet there is no single definitive statement regarding whether or not COVID-19 can be transmitted via air. There is also no evidence that the virus can be spread via air conditioning as of yet, beyond the laboratory sampling of the Diamond Princess suites.
What is interesting to note is that while patterns of spread are consistent with transmission through droplets from one infected person to another, patients are currently being treated in the hospital setting in specialised ‘negative pressure rooms’ and doctors and nurses are taking ‘airborne precautions’ when performing procedures. This involves putting up makeshift barriers made of plastic, and protecting one’s face and body from any potential escaped droplets. It also involves protecting healthcare workers during any ‘aerosol generating procedures’, such as suctioning airways, ventilation and “induced” sputum.
So what does the World Health Organization say about the possibility of COVID-19 being an airborne disease? It maintains that the virus spreads directly from person to person when a COVID-19 case coughs or exhales producing droplets that reach the nose, mouth or eyes of another person. Its latest reports also states, “According to the currently available evidence, transmission through smaller droplet nuclei (airborne transmission) that propagate through air at distances longer than 1 meter is limited to aerosol generating procedures during clinical care of COVID-19 patients.”
Recent evidence that the virus can survive outside the human body on surfaces like metal, glass and plastic for as long as nine days, unless they are correctly disinfected, brings the notion of COVID-19 being transmittable only via person-to-person contact into serious question. Testing on similar respiratory viruses, like MERS and SARS, found that some can even hang around for up to 28 days in particularly low temperatures. We also know that the measles can survive in a room for up to 30 minutes on its own, and that the MERS coronavirus has been captured in infectious form in hospital air samples previously. Evidence has also found that the virus can shed longer in faecal matter, so slowly health authorities are warming up to the fact that transmission isn’t necessarily a straightforward matter of person-to-person contact.
The simple answer is that there is no simple answer to the question of whether the COVID-19 virus can be transmitted via air conditioning. Until we do know for sure, however, it pays to play it safe. Like all things, maintain a strong hygiene and sanitation regime. Clean your house – and hands – as much as possible, and minimise contact with others until this whole thing passes. For the time being, that is the only thing we know is proving effective in the war against the novel coronavirus.