Covid-19: Virus spreads through air; UAE doctors’ urge caution
Citing ten reasons it is transmitted by air, authors call for urgent modification of safety protocols.
UAE doctors have called on residents to strictly follow safety measures after a report by The Lancet says SARS-CoV-2 is an airborne pathogen.
The paper, written by six experts from the UK, the US and Canada have cited ten reasons why SARS-CoV-2 is transmitted primarily by air, debunking the earlier predominant scientific view that the coronavirus that causes Covid-19 is not an airborne pathogen.
Arguing that there are ‘insufficient grounds for concluding that the pathogen is not airborne’ they have also called for an urgent modification of the established Covid-19 safety protocols.
In response to the report, UAE doctors have said in addition to following the basic health and safety protocols such as regular hand washing, mask-wearing, and physical distancing; the general public must also become more aware and more cautious of several other factors that could cause the virus to spread.
Dr Igbal Mubarak Sirag, specialist internal medicine at Bareen International Hospital, MBZ City, said “If a virus is airborne, there is a higher risk of infecting others through inhalation of aerosols produced when an infected person exhales, speaks, shouts, sings, sneezes, or coughs.”
He said the public must also factor in reasons such as air ventilation, air filtration, reducing crowding and time spent indoors, use of masks whenever indoors, attention to mask quality and fit, and higher-grade protection for healthcare staff and frontline workers.
Dr Rajesh Kumar Gupta, specialist internal medicine at Burjeel Speciality Hospital, Sharjah, said, “The latest Lancet systemic review strongly favours the airborne transmission of SARS-CoV-2 since viable viral particles have been isolated from air filters, air-conditioning ducts, car-air/ room-air samples of an infected person and adjacent room-air, nosocomial infection among healthcare staff.” He added, “Therefore, an infectious virus is mainly airborne, an individual could potentially be infected when they inhale aerosols produced when an infected person exhales, speaks, shouts, sings, sneezes, or coughs.”
Dr Gupta said, “Speaking produces thousands of aerosol particles and few large droplets, SARS-CoV-2 stayed infectious in the air for up to 3h with a half-life of 1·1h, which supports the airborne route. Reason is the overwhelming number of aerosols produced in respiratory activities and the arbitrary boundary in particle size of 5m between aerosols and droplets, instead of the correct boundary of 100m and smaller aerosols showed higher pathogen concentrations than droplets when both were measured.”
“So, there is consistent, strong evidence that SARS-CoV-2 spreads by airborne transmission. Although other routes can contribute, the airborne route is likely to be dominant,” he added.
Reducing the airborne transmission of the virus requires measures to avoid inhalation of infectious aerosols, including ventilation, air filtration, reducing crowding and time spent indoors, use of masks whenever indoors, attention to mask quality and fit, and higher-grade protection for health-care staff and front-line workers are safekeeping measures Dr Gupta suggests.
However, Dr Payal Modi, microbiologist and head of infection control, NMC Dubai Investment Park (DIP — Hospital, Dubai), said that proving one mode of transmission over another can be a daunting challenge. “Following simple points still substantiate that airborne transmission is questionable. Firstly, physical distancing would certainly not work, and clusters of cases would arise where there was no obvious close contact with those infected,” she said.
“Widespread use of surgical masks, which generally only protect against large droplets unlike N95 respirators which block at least 95 per cent of 0.3-micron particles has not been associated with increased Covid-19 in healthcare workers. A breach in other infection control measure should also be ruled out before concluding the fourth and fifth point in the Lancet report,” she added. “Low secondary rates of infection have been observed when people share meals or within households. A higher incidence of infection would be expected if the airborne transmission was a contributing factor,” she said.
Some reasons cited in Lancet report:
>> ‘Superspreading events account for substantial SARS-CoV-2 transmission; indeed, such events may be the pandemic’s primary drivers.’ According to the authors, detailed analysis of human behaviours and interactions, room sizes, other variables are consistent with the airborne spread of SARS-CoV-2. The report states that the same cannot be fully explained by droplets or fomites.
>> ‘Long-range transmission of SARS-CoV-2 between people in adjacent rooms but never in each other’s presence has been documented in quarantine hotels,’ the paper said.
>> Authors argued that 33 per cent to 59 per cent of all coronavirus cases can be attributed to the asymptomatic or pre-symptomatic transmission without the infected person coughing or sneezing. >> The authors wrote that the transmission of the pathogen is higher indoors compared to outdoors. Transmission is substantially reduced by indoor ventilation, according to the authors. The report reads that nosocomial infection (those that originate in a hospital) have been detected even in places where healthcare professionals wore PPE to protect themselves against the virus transmission through droplets.
>> The authors state that viable SARS-CoV-2 has been detected in the air. During laboratory experiments, the pathogen stayed infectious in the air for up to three hours.
>> The experts argued that the pathogen has been detected in air filters and buildings ducts in hospitals with COVID-19 patients in them. “Such locations could be reached only by aerosols,” they said. The authors cited studies conducted on infected caged animals that showed SARS-CoV-2 being transmitted via an air duct.
>> The experts stated that there is no study to their knowledge that provides strong or consistent evidence that disproves their hypothesis. The final argument was that there was limited evidence that supports other dominant routes of SARS-CoV-2 transmission.
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