COVID-19 SPECIAL

239 scientists flag risk of airborne transmission of coronavirus

Revellers gathering in London's Soho area on Saturday, after pubs in England reopened that day for the first time since late March. Experts in Singapore say safe distancing and hygiene measures already in place here are generally sufficient to keep t
Revellers gathering in London's Soho area on Saturday, after pubs in England reopened that day for the first time since late March. Experts in Singapore say safe distancing and hygiene measures already in place here are generally sufficient to keep the virus in check, even if it is possibly airborne. PHOTO: AGENCE FRANCE-PRESSE

They seek new safety guidelines from WHO but local experts say no cause for panic

While airborne transmission of the coronavirus is a possibility, experts here say it is not cause for panic, and that safe distancing and hygiene measures already in place in Singapore are generally sufficient to keep it in check.

This comes as 239 scientists from 32 countries signed an open letter to the World Health Organisation (WHO), calling for a new set of safety recommendations in the light of evidence that the virus can travel farther and remain suspended in the air for longer, The New York Times (NYT) reported.

WHO has said since the start of the outbreak that the virus spreads mainly through small droplets from the nose or mouth, which are relatively heavy, do not travel far and quickly sink when an infected person coughs, sneezes or speaks. So it has promoted handwashing and social distancing as a primary strategy to prevent contagion.

If airborne transmission plays a significant role, NYT said on Saturday, masks may be needed indoors, even in socially distant settings, and healthcare workers may need N95 masks that filter out even the smallest respiratory droplets as they care for Covid-19 patients.

Doctors and researchers here say this is already being done in Singapore, and whether the scientists in the open letter are correct or wrong should not impact the way the country responds to the virus.

Dr Kristen Coleman, a research fellow at Duke-NUS Medical School's emerging infectious diseases programme, pointed out that aerosol transmission is not a problem to be feared.

"The (Government) has appropriately provided everyone with face masks and mandated their use in public, along with physical distancing and limiting social gatherings to five people."

Her advice: "The best thing people can do is to keep this transmission pathway in mind and follow all measures already put forth, especially if they plan to dine-in at restaurants or host small gatherings at home during phase two of reopening.

"I would strongly encourage people to do this outdoors or in well-ventilated spaces, if possible, and to of course continue frequently washing hands with soap and water to minimise contact transmission."

The open letter is set to be published in a scientific journal later this week.

Experts that NYT spoke to said WHO has been out of step with science, and slow and risk-averse in updating its guidance.

 
 

But local infectious diseases expert Leong Hoe Nam told The Straits Times that the WHO's response is necessarily slow as it can act only when there is almost irrefutable evidence.

"There are many things which are unknown. The complication from a misstep is someone's death," said Dr Leong, who practises at Mount Elizabeth Novena Hospital.

He noted that there is some evidence for the virus being able to linger in the air, and that given that Covid-19 is a new disease, taking a more risk-averse approach to tackling it is justifiable.

However, he also pointed out that places such as Taiwan, Hong Kong and Japan have been able to control the number of cases without operating under the assumption that the virus is airborne. Singapore, too, had kept case numbers small and manageable so far simply with the use of masks, social distancing and clean hands, he added.

"This means that there are many factors at play, and attributing the virus' spread entirely to it being airborne is placing an inappropriate amount of blame on one factor."

Stressing that the key to tackling the virus is about compliance with mask-wearing rather than worrying about airborne transmission, he said: "We don't need to participate in this discourse just because (other countries) have poor compliance with measures."

A public health expert here, who declined to be named, shared a similar sentiment.

He said: "If you look at what we are doing in Singapore, wearing masks both indoors and outdoors, keeping social distances, limiting the number of people within indoor spaces - all these are effective whether spread is by objects which carry infection or by aerosol.

"We can attempt to improve ventilation or air exchange in buildings, but there are limits to what is practicable in Singapore."

 
 

Professor Wang Linfa, director at Duke-NUS Medical School's emerging infectious diseases programme, said that while there may have been cases of infection arising from aerosol transmission, to claim it is a significant route of transmission may be an overstatement in the absence of solid new data.

Dr Coleman pointed to an earlier study where local researchers had detected the coronavirus in the air of infected patients' rooms, but had been unable to assess how infectious it was in such samples.

"That is part of what is keeping WHO and others from acknowledging the risk of aerosol transmission."

ST has contacted the Ministry of Health and the National Centre for Infectious Diseases for comment.

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A version of this article appeared in the print edition of The Straits Times on July 06, 2020, with the headline '239 scientists flag risk of airborne virus'. Print Edition | Subscribe