What does Covid-19’s latest mutation mean, and what exactly is behind the raging debate over airborne transmission that has the WHO under fire.

With lockdown restrictions being eased around the world, scientists and governments are faced with a new challenge: how common are airborne-transmitted infections of Covid-19?

SARS-Cov-2 is a respiratory infection. It can be spread directly when one comes into contact with it - this can be either when someone touches a surface where the living virus exists, or via the droplets caused by coughs, sneezes or airborne particles. Droplets usually come in the form of a viral load, a mix of  mucus and saliva, when someone coughs or speaks. They can be as large as a grain of sand, or as small as a red blood cell which is five microns wide.

To give that a comprehensive scale, a human hair is about 75 microns wide.

Most droplets cannot travel further than one or two metres, usually falling to the ground within seconds. If someone becomes ill after being exposed to an infected cough, the blame would be placed at the door of droplet transmission.

Then there is the third method, the hotly debated one: airborne transmissions.

Airborne transmission can occur from even smaller particles - these are called droplet nuclei - formed when people speak, or when larger droplets evaporate, causing them to float as an aerosol.  

This is significant because it means that the virus could stay in the air for hours, and it goes against the World Health Organization (WHO) position that Covid-19 is spread through large droplets caused by sneezes and coughs that quickly fall onto the floor.

Precautions or reality?

In an open letter to the WHO, 239 scientists from 32 countries provided evidence that lingering aerosolized particles can also infect people, calling for a revision of public health recommendations.

The WHO’s Infection Prevention and Control Committee is coming under fire for its rigid, slow approach to updating public safety recommendations, and this is not the first time it has come under pressure.

In April, more than thirty experts on aerosols and airflow, requested the organisation to pay more attention to the growing evidence on airborne infections. They, however, were dismissed by conservative internal experts who favoured handwashing.

Semantics?

Dr. Lidia Morawska who spoke to the New York Times, believes the WHO is making an unnecessary distinction “between tiny aerosols and larger droplets, even though infected people produce both.”

The WHO’s argument remains that the virus has not been able to grow in the tiny particles found in aerosols which are developed in labs. But, say many scientists, this does not mean aerosols are not infectious.

It may come down to methods of experimentation. Hospitals usually have good airflow by design, and this would lower viral loads making it harder to measure in an experimental setting. Most buildings, however, have lower air-exchange rates, letting viral particles accumulate - this will present a greater risk.

To compound the problem, many believe the WHO is using an old definition of airborne transmission.

Dr. Khalid Desin, a postdoctoral virologist researcher at the University of Saskatchewan, Canada, spoke to TRT World to clarify the controversy.

“When we think of airborne transmissions, we assume it's something that stays in the air for hours. That could be the case, but more often it's a viral load delivered at close range in enclosed spaces,” he says.

The controversy could be mired in practicality. If the WHO expanded its measures for public safety, it could see countries that are already struggling to meet essential needs dedicate further resources to something they believe is at best, precautionary.

For many epidemiologists, precautions should be expressed for the sake of clarity.

“It’s not all bad news,” says Dr. Desin. “While some studies do show that the virus can stay alive in the air anywhere between 4 to 16 hours, what they don’t tell you is that sunlight usually kills the virus within 7 minutes of exposure. The risk is in-doors.”

Racing against the clock

A mutated Covid-19, discovered as early as April 2020, is now considered the dominant infection sweeping the globe after a new study was published in the journal Cell last Thursday.

Anthony Fauci, one of the most prominent infectious diseases expert in the United States, commented, “I think the data is showing that there is a single mutation that actually makes the virus be able to replicate better, and maybe have high viral loads."

He cautioned against fears of whether the mutation is more lethal or not, which was still trying to be determined.

“It just seems that the virus replicates better and may be more transmissible,” added Fauci.

The mutation was relatively small. One protein on the virus’s surface, containing nearly 1,300 amino acids, saw a change in the genetic code of one of those amino acids.

The result? The activation of a “spike protein”, which gives the virus its distinct shape, allows it to break into human cells and further spread itself.

A study conducted in UC San Francisco, since published in the journal Cell, reveals disturbing details. In rather sinister fashion, once a cell is invaded and infected, it sprouts multi-pronged tentacles carrying viral particles, which reach out and poke into neighboring healthy cells, injecting new genetic instructions.

Previously, Covid-19 was thought to infect cells by the way it bound itself to receptors on cells which line our mouths, noses, lungs and blood vessels.

The new mutation gives the virus “4 to 5 times more” ‘spikes’, allowing it to latch on to cell receptors more easily than before, although the report describing the amount of spikes is still under peer review.

Mutations are significant to scientists and virologists - they fear a radical change in Covid-19’s structure might ultimately hinder the development of a much-needed vaccine.

Public health officials and governments, meanwhile, are growing concerned that a more infectious or lethal mutated form of the virus could arise before a cure is found.

Source: TRT World