NCID studying to see if coronavirus naturally airborne

Since the start, WHO has stuck to its stance that the coronavirus is primarily transmitted via contaminated droplets.
Since the start, WHO has stuck to its stance that the coronavirus is primarily transmitted via contaminated droplets.ST PHOTO: LIM YAOHUI

But even if it is, current measures in place here sufficient to curb transmission rates: Expert

The National Centre for Infectious Diseases (NCID) is carrying out a study to determine if the coronavirus is naturally airborne, and infectious in such a form.

But even if it is, the current measures in place here would be sufficient to reduce transmission rates, NCID senior consultant Kalisvar Marimuthu said yesterday.

He was responding to queries on an open letter signed by 239 scientists around the world, calling on the World Health Organisation (WHO) to acknowledge the risk of the virus that causes Covid-19 being airborne. The letter is expected to be published in a scientific journal this week.

Since the start of the outbreak, WHO has stuck to its stance that the coronavirus is primarily transmitted via contaminated droplets, which are relatively heavy and do not remain in the air for long.

But one of the scientists, Dr Linsey Marr, told The Straits Times that WHO has an "outdated understanding of aerosols".

Experts agree the coronavirus does not spread the same way a stereotypical airborne virus does - floating down the streets for many hours and infecting people as it moves in and out of homes.

But Dr Marr and her peers say it does travel much farther than the 1-2m expected of a droplet-borne illness, putting people in prolonged contact at close range, especially indoors, at risk.

Dr Marr, a professor of civil and environmental engineering at Virginia Tech in the United States, said she and her peers decided to write the letter as they felt that WHO and other public health agencies were not paying proper attention to the potential for the airborne spread of the coronavirus in situations of close contact and in crowded indoor environments with poor ventilation.

She added: "If these agencies were to recognise this route of transmission, then they could have addressed it through mitigation strategies such as mask-wearing, social distancing and improved ventilation of buildings, along with hygiene. This would have slowed the spread of Covid-19."

Dr Marr and her fellow scientists said that in the light of evidence that the virus spread could be airborne, the public should consider social distancing, wearing face coverings such as masks, avoiding crowds, ensuring good ventilation with outdoor air and looking after their own hygiene.

But Dr Kalisvar told The Straits Times that researchers here have not seen sufficient strong evidence to place Sars-CoV-2 - the virus which causes Covid-19 - in the same category of airborne viruses as measles, chickenpox and tuberculosis.

 
 
 

He acknowledged that the virus can be aerosolised during specific procedures in hospitals, and said a recent NCID study had shown parts of the coronavirus existing in particle sizes smaller than four microns.

Typically, viruses present in particles that are smaller than five microns are considered capable of being transmitted through air.

But Dr Kalisvar said the main issue is the significance of such a transmission mode for Covid-19.

NCID senior consultant Kalisvar Marimuthu said that researchers here have not seen sufficient strong evidence to place Sars-CoV-2 - the virus which causes Covid-19 - in the same category of airborne viruses as measles, chickenpox and tuberculosis.

Dr Kalisvar also emphasised that even if the virus has been shown to be transmitted via aerosol in certain situations, such as singing, measures such as hygiene, safe distancing and compulsory mask-wearing are already in place here and would still work to reduce such transmission.

 
 

"At this stage, there isn't sufficient evidence to prove that the virus is naturally aerosolising and infectious (in such a state)," he said, adding that NCID is carrying out experiments in airborne infection isolation rooms and in communal living settings to study if the virus is viable in the air.

He also emphasised that even if the virus has been shown to be transmitted via aerosol in certain situations, such as singing, measures such as hygiene, safe distancing and compulsory mask-wearing are already in place here and would still work to reduce such transmission.

"So we should increase our adherence to existing community infection prevention and control measures outlined by the Ministry of Health," he added.

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A version of this article appeared in the print edition of The Straits Times on July 07, 2020, with the headline 'NCID studying to see if virus naturally airborne'. Print Edition | Subscribe