Evidence Emerge Coronavirus Has Airborne Transmission, But Its Scope, Dangers Yet Unclear

Evidence Emerge Coronavirus Has Airborne Transmission, But Its Scope, Dangers Yet Unclear

As more evidence of airborne or aerosol transmission of the novel coronavirus causing the COVID-19 lung disease emerge, the World Health Organization (WHO) has updated its guidance in a way that does not rule it out in settings other than healthcare facilities but urged more research as its significance as a route of infection and epidemiological risks remain in question

MOSCOW (Pakistan Point News / Sputnik - 10th July, 2020) As more evidence of airborne or aerosol transmission of the novel coronavirus causing the COVID-19 lung disease emerge, the World Health Organization (WHO) has updated its guidance in a way that does not rule it out in settings other than healthcare facilities but urged more research as its significance as a route of infection and epidemiological risks remain in question.

On Thursday evening, WHO published an updated scientific brief on the modes of transmission of COVID-19. The 10-page document outlines what has been learnt so far about how the virus transmits.

Whereas the document maintains that close contact with a symptomatic person, who expulses droplets with the virus when sneezing and coughing, and contaminated surfaces remain the most common routes of transmission, it also looks at the so-called airborne or aerosol transmission. In this case, a susceptible individual gets infected through much smaller droplets, less than 5 microns (or 0,001 millimeters), which could remain airborne and travel larger distances.

Previously, the UN health body asserted that such type of transmission was mostly occurring in medical facilities using aerosol-generating procedures, but the updated brief acknowledged reports of infections in other crowded indoor settings that could have been caused by this mode of transmission. In such instances, the virus could have been transmitted by these small droplets expulsed by an infected individual through breathing and talking along with larger droplets through close contact. Such settings, including to WHO, included choir practice, in restaurants or in fitness classes.

"In these events, short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out. However, the detailed investigations of these clusters suggest that droplet and fomite transmission could also explain human-to-human transmission within these clusters," the document read.

"Further, the close contact environments of these clusters may have facilitated transmission from a small number of cases to many other people (e.g., superspreading event), especially if hand hygiene was not performed and masks were not used when physical distancing was not maintained," it added.

According to WHO, though a susceptible individual can get infected by these microdroplets, their proportion and the dose of the viable SARS-CoV-2 virus causing COVID-19 needed to cause infection are unknown.

The WHO brief followed an open letter signed by more than 200 scientists, who urged national and international health organizations to recognize the potential of airborne transmission. According to scholars, hand washing and social distancing - predominant preventive measures lauded by health officials and organizations across the globe - are insufficient to protect people from getting infected with virus-carrying microdroplets, especially in indoor spaces with inadequate ventilation.

Normally, this mode of transmission is verified in diseases using "indirect methods," i.e. when a subject becomes infected in such circumstances, but it is hard to do in the case of COVID-19 because airborne transmission can occur from asymptomatic or pre-symptomatic individuals who are difficult to detect, Professor Santiago Mas-Coma, the president of the World Federation for Tropical Medicine and an expert member of the World Health Organization, explained to Sputnik.

"But when a virus is transmitted by droplets, given the very small size of a virus, it is evident that it may be transmitted by both big and small droplets," Mas-Coma, who also works as director of parasitology at the University of Valencia, said.

"Transmission by small droplets transported by the wind in an open environment is negligible, but the capacity of air conditioning to expand small droplets to longer distances inside a closed environment or building has been verified and should not be overlooked," the expert stressed.

Mas-Coma noted that this, in turn, highlighted the importance of use of proper filters in air conditioners, repeated disinfection of surfaces, wearing a mask inside air-conditioned places, including shops and warehouses, as well as public transport, which the expert described as "risky" setting.

At the same time, physical distancing and wearing a mask remained valid public health measures, according to the expert.

"Security distances of 2 meters when you talk to an asymptomatic person and 5 meters when with a person with strong sneeze and/or cough, continue to be valid measures. And everybody wearing mask continues to be the most effective measure. A mask is not only for self-protection, but also to protect the others, because a mask is a barrier for the droplets for both exit and entry," Mas-Coma said, noting that a mask's effectiveness in stopping the small droplets depended on filters used in it.