Scientists call on WHO to raise the bar, says S.Ananthanarayanan.

239 scientists have called upon the World Health Organisation to include the airborne path as a transmission route of SARS-CoV-2, to serve as basis for due measures to be taken, worldwide.

The ‘open letter’ to WHO is in the form of a ‘commentary’, dated 6th July 2020, in the >, of the Infectious Diseases Society of America, by Lidia Morawska from the International Laboratory for Air Quality and Health, Queensland Institute of Technology, Australia, and Donald K. Milton, from the University of Maryland School of Public Health, USA.

The letter, which is endorsed by 239 scientists, opens with the words, “We appeal to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of COVID-19. There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (micro-droplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission.”

WHO guidelines, to date, are limited to transmission through respiratory droplets. Many kinds of viral, bacterial or fungal infections spread through respiratory droplets. These are the liquid specks of saliva, mucus, sputum, which are expelled when a person coughs, sneezes or even speaks loudly. They droplets could originate from different parts of the respiratory tract and could be laden with viruses and bacteria. They are typically more than 5 microns (thousandths of a millimeter) wide and if they reach sensitive areas, like the eyes, within the nose or the mouth of another person, they would transfer the infection. Examples of viruses transmitted in this way are the flu, the common cold, infections of the bronchial or respiratory track, disease of the intestines, even measles and chicken pox. And COVID-19 has been treated, by WHO, as one more.

Traditionally, it is nearly visible droplets, more than 5 microns wide, which have been studied and they are known to fall to the ground, or other surfaces, within a metre or two. The first precautions that WHO recommended, in respect of SARS-CoV-2 were hence that people keep a distance of two metres. And, as viruses deposited on surfaces can be viable for many hours, not to touch exposed surfaces, to wash one’s hands and avoid touching one’s face.

There had been studies that suggested that the virus was also spread by aerosols, or smaller droplets, which did not settle, but stayed airborne for minutes and hours. This is the way influenza or measles are spread. These studies had come to the notice of the WHO and they did evaluate what had been reported. But WHO found no evidence of COVID-19 spread by aerosols and on 27th March 2020, they published a ‘scientific brief’, Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations (IPC stands for Infection Prevention and Control). The brief concluded that the spread by aerosols was limited to ‘specific circumstances and settings’ which gave rise to aerosols, specifically, when dealing with patients, during procedures like working with the bronchi or tracheae of patients or during inserting and removing ventilator devices.

As for the studies that reported persistence of the virus, WHO observed that these are with artificially generated aerosols in a laboratory setting and did not represent normal conditions of human aerosol generation. “In analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported,” the report said. Strangely, the report stresses that there are “settings with symptomatic COVID-19 patients in which no COVID-19 RNA was detected in air samples.” And then, that where traces of RNA have been detected, it is not clear that there were viable viruses.

The evidence of airborne transmission, however, has continued to be found and on 27th May, the journal, Science carried an article citing recent studies, including one where Lidia Morawska, an author of the appeal to WHO, with G. Buonannoa and L. Stabil, from the Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Italy, had quantified the viral load emitted by infected persons under controlled conditions. The results of the study, which disposes of the WHO remark that lab studies did not reflect real life, surprisingly showed that an asymptomatic person could reach high virus emission levels while vocalising, in the course of just slowly walking.

This is in keeping with other studies cited by Science, which showed that asymptomatic persons were “highly contagious for several days, peaking on or before symptoms occur, and could be critical drivers of the spread of SARS-CoV-2. The paper in Science hence drew attention to this unseen, airborne presence of the virus, and, with more instances of high airborne emission, and the record of the best results in places where universal masking was ordered, recommended the use of masks, certainly in enclosed spaces.

The Statesman carried a report,on this paper in Science, in its issue of 3rd June 2020

In the meantime, despite extended lockdown in all parts of the world, and despite restrictions when services are resumed, there is no sign of the pandemic abating. The appeal of the group of scientists is hence that governments and communities recognise that there are more ways than direct contact and close approach to spread the infection. The appeal refers to 17 authoritative studies, with established results, and some as recent as May and June, to assert that “several retrospective studies conducted after the SARS-CoV-1 epidemic demonstrated that airborne transmission was the most likely mechanism explaining the spatial pattern of Infections… …retrospective studies have shown the same for SARS-CoV-2.”

The appeal cites an instance of three independent families who dine at a restaurant. Members of two of the families were found to have been infected, from a suspected source in the restaurant. Simulation of the movement of the air in the restaurant demonstrated that the infection instances were in keeping with the air having transferred aerosols exhaled by the source to the persons infected, but not to the family which was not. “Airborne transmission appears to be the only plausible explanation,” of this and other instances, the appeal says.

It grants that the ‘evidence’ of transmission by aerosols is not complete, but this is the same with droplets and fomites. The WHO guidelines warn against droplets and fomites, but why not the pathway of airborne transmission? “In our collective assessment there is more than enough supporting evidence…. in order to control the pandemic, pending the availability of a vaccine, all routes of transmission must be interrupted,” the appeal says. It is therefore important, the appeal says, that airborne route of the infection be officially recognized

Communities follow Government instructions and governments need authorities like the WHO, before they commit themselves. WHO, in reaction to the letter from the scientists, has granted ‘the possibility of airborne infection,’ but not more. There would be procedures the organization needs to follow before they act to make the declaration. This, however, should not deter the community from paying heed, in its own best interest!

Recommendations in the open letter
It is vital, now that states are reopening workplaces, schools and colleges, that there is awareness of the risk of airborne transmission. One important measure is effective ventilation – clean air, the least re-circulation. “Simple steps like opening both doors and windows can dramatically increase air flow rates in many buildings.

Ventilation and AC engineers in the US and Europe, the letter says, have issued guidelines to control air quality. These need to be adapted to systems in India, so that getting back to work does not lead to further peaks of infection

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