The World Health Organization said Tuesday that it would reconsider its longtime stance that airborne transmission of the SARS-CoV-2 virus occurs only rarely – after a group of over 239 scientists published a commentary on Monday in the Journal of Clinical Infectious Diseases, urging the agency to acknowledge the greater role played by tiny virus particles emitted from route breathing and speech in driving COVID-19’s spread.

Currently, WHO maintains that the main route of virus transmission is via larger droplets – expelled by people coughing and sneezing at close range into the noses, mouths, and eyes of uninfected people nearby.

While the distinction may seem esoteric to some – it is critical to disease control policy decisions. Since most large, liquid droplets fall quickly to the ground, assuming disease spread is via droplets has also precluded a strong WHO position on the usefulness of masks, or on the infection risks within indoor settings, from restaurants to offices.

“We have been engaged with this group since April, when they first wrote to us,” said WHO COVID-19 Technical Lead Maria Van Kerkhove. “We have been talking about the possibility of airborne and aerosol transmission, as one of the modes of transmission of COVID-19, as well as droplets, fomites [surface contamination], fecal-oral, mother-to-child, and animal-to-human transmission. We are producing a scientific brief summarizing where we are… [and] we will be issuing our briefing in the coming days.”

“We acknowledge that there is emerging evidence in this field… regarding the COVID-19 virus and pandemic, and therefore we believe that we have to be open to this evidence, and understand its implications regarding [the virus’] mode of transmission and precautions that need to be taken,”  added Benedetta Allegranzi, Infection Prevention and Control Lead at WHO.

Some of WHO’s recommendations already account for the possibility of airborne spread of the virus, according to WHO Chief Scientist Soumya Swaminathan, speaking at the press event. For example, WHO recommends avoiding crowded settings and ensuring proper ventilation in indoor areas.

However experts interviewed by Health Policy Watch and other media have complained that WHO’s guidelines are based on out of date evidence, overly rigid and medicalized – thus failing to account for the rapidly evolving evidence about virus transmission via tiny airborne particles that can travel much further than liquid droplets, remain suspended for longer in the air, and spread further over time closed or poorly ventilated rooms.

“The infection control folks sort of helping WHO set their policies think of particles in two ways – Droplets, which are very large, or…. small droplet nuclei, which is their term for particles in air… the can travel far from the source,” said Lisa Brosseau, an industrial hygienist studying aerosol transmission at the Center for Infectious Disease Research and Policy. “What they don’t seem to recognize in that dichotomy, is that when you cough and sneeze and talk and breathe, you actually generate lots of smaller particles.”

“Personally, I think the WHO should stop arguing what looks like semantics to much of the outside world. Science adapts to new information,” Stephen Morse, emerging infectious disease epidemiologist and influenza expert at Columbia University told Health Policy Watch. “The terminology is terribly confused, and therefore unfortunately leads to a great deal of confusion.

“When someone sneezes, coughs, talks loudly, etc., it generates a range of particles. The larger ones are droplets, which are fairly heavy and generally go only a short distance before falling to the ground (hence the “6 ft” rule).  Finer particles can stay in the air longer and go further; some can stay airborne for long periods and go long distances in the wind (remember the Sahara dust that just passed our way?). Unfortunately, the varying definitions give people the wrong impression that there is some sort of dichotomy.  It’s not an ‘either/or’.

“In my opinion (nothing more), infection probably does occur by both droplets and fine particles [that can remain suspended in air], but we don’t know how important each is.  And since there’s a distribution of particle sizes, the answer may not be quite so simple, either.

“The confusion may arise, in part, from the distinction between “droplet” and “airborne” transmission made by infection control practitioners [in hospital settings]. I think the problem is that they didn’t have better words to use when they were developing the guidelines,” said Morse.

Experts Head to China in Quest for Animal Sources of the Virus

In a parallel development, WHO scientists will also be going to China this weekend in order to track down the zoonotic origins of COVID-19, Dr Tedros announced. The WHO team will be collaborating with Chinese counterparts to define a scope of work and terms of reference.

“The mission objective is to advance the understanding of animal hosts for COVID-19 and ascertain how the disease jump between animals and humans,” said Dr Tedros.

Still, hunting down the animal origins of the virus is not as simple as it sounds. The virus may circulate in some host animals in the wild, and then pass through other animals that are more likely to pass the disease onto humans. These so-called ‘intermediate hosts’ can be difficult to identify, according to WHO Executive Director of Health Emergencies, Mike Ryan.

“The narrative of this virus into the human population is extremely important, but it’s not always a straightforward process of being able to get that answer. I know that sounds obtuse, but there are many dead ends to study these things,” said Ryan. “We spent many years trying to look up the source for Ebola and the intermediate host, and we still, even in Ebola, have difficulties with identifying the intermediate hosts.”

Brazilian President Contracts COVID-19 After Months Of Scorning Measures To Slow The Pandemic

Meanwhile, as new COVID-19 cases continued to rise sharply in the Americas and India – the latest global hotspots – WHO  Director General Dr Tedros Adhanom Ghebreyesus told reporters that the world has “not yet reached the peak of the pandemic” .

His dire warning came as Brazil’s President Jair Bolsonaro tested positive for COVID-19 and more than 400,000 new COVID-19 cases were reported worldwide over the past weekend. In comparison, it took 12 weeks for the pandemic to hit the first 400,000 cases.

Bolsonaro’s infection came after months in which his government continually downplayed the seriousness of the COVID-19 pandemic, even while Brazil now has the largest number of confirmed cases in the world, second only to the United States, with India trailing in third place.

In a fairly dismissive announcement of his test results, Bolsonaro declared on Brazilian national television Tuesday that “everyone knew that it would reach a considerable part of the population sooner or later.

Image Credits: Columbia University Mailman School of Public Health, Johns Hopkins CSSE.