A scientist, who was one of 239 signatories to a letter to the World Health Organization over concerns Covid-19 could be an airborne virus, has called on the UN health body to update its guidance.
The WHO has previously said the virus spreads primarily through small droplets expelled from the nose and mouth of an infected person that quickly sink to the ground.
But in an open letter to the Geneva-based agency, published on Monday in the Clinical Infectious Diseases journal, 239 scientists in 32 countries outlined evidence that they say shows floating virus particles can infect people who breathe them in.
When an infected person exhales, they expel droplets. Droplets under five micrometres in size can become suspended in the air for several hours and travel up to tens of metres, they said.
Speaking on RTÉ's Today with Sarah McInerney, Professor John Wenger said there needs to be greater recognition of the route of aerosols from exhaled breaths in the transmission of Covid-19.
The Professor of Chemistry at UCC said a large body of evidence shows that exhaled breath releases smaller particles that can travel further and remain in an indoor environment for a few hours.
He said that this could be an important transmission route under certain conditions, such as in crowded or poorly ventilated areas and while it may not be the dominant pathway for the virus, it is a viable one.
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Prof Wenger said the WHO could add a few extra measures to its guidelines; such as avoiding high room occupancy and spending a lot of time indoors (unless wearing face masks) and increasing ventilation.
He added that the issue of ventilation has not been covered much by the WHO and simply opening doors and windows may be useful, which must be considered as schools reopen in September and people who are currently remote working return to offices.
Prof Wenger said face coverings and good hygiene, including cough and sneeze etiquette, will be very important but each case must be looked at individually.
He said SARS had been an airborne virus and travelled in the same way.
A specialist in infectious diseases said he believes the airborne theory is a credible theoretical hypothesis, but the jury is still out and it is not known what proportion of new cases are caused by aerosols.
Professor Sam McConkey said it is hoped that the viral load in an aerosol from an exhaled breath is tiny and that people would be at less likely to acquire the disease via aerosol and that if they did, they may become less ill, but this is an unknown.
Speaking on the same programme, he said that it would be good for the WHO to review the evidence.
Prof McConkey said there are many different specifications to face masks and if the airborne theory is borne out, then those in healthcare settings might need to wear special high filter masks.
He said it would great to find new additional things [about the virus] that do not interfere with our lifestyles and help us relax the more restrictive measures currently in place.
The World Health Organization says data to date suggests 80% of Covid-19 infections are mild or asymptomatic; 15% are severe infection, requiring oxygen and 5% are critical, requiring ventilation.
Generally, you need to be 15 minutes or more in the vicinity of an infected person and within two metres of them, to be considered at-risk, or a close contact.
Additional Reporting Reuters
