Coronavirus cannot be spread through air, WHO confirms

This is reflected in the latest report of the World Health Organization entitled "Modes of transmission of the virus causing COVID-19", which clarifies how the virus is transmitted and how it is not transmitted, through air and other means, although some experts suggest that it is possible and it is recommended that physicians and nurses take precautions.

So far we know that for the transmission of the virus to take place, the infected person must be a metre away from another and cough or sneeze. This is a risk of contagion. Additionally, the new coronavirus can also spread if it touches a surface previously touched by a patient infected with the virus or touches tools or objects used by the patient, such as a thermometer.

WHO explains that airborne transmission occurs when there are microbes within the droplet cores, which may remain in the air for long periods of time and may be transmitted over a distance of one metre and, therefore, to infect others. However, there is little scientific evidence of its transmission by air except in very specific cases during hospital treatments such as endotracheal intubation, bronchoscopy, manual ventilation prior to intubation, tracheostomy or cardiopulmonary resuscitation, amongst others.

Contradictory study

However, a study by more than a dozen health experts working side by side with the Rocky Mountain Laboratories of the United States National Institute of Health found that "The aerosol transmission of SARS-Cov-2 is plausible, as the virus may remain viable and infectious in aerosols for hours".

The research, published in the New England Journal of Medicine, exposes that the virus could have spread through the air in a church in Washington State (Mount Vernon Presbyterian Church) where a choir rehearsal in early March was considered the cause of a fatal coronavirus outbreak, says Jamie Lloyd-Smith, a UCLA professor and infectious disease researcher.

Another study conducted in Singapore in early March also suggested "that small droplets loaded with viruses can be displaced by air flows and deposited in equipment such as vents". Additionally, a peer-reviewed study from China stated that the intensive care unit, the coronary care/cardiac unit and the general patient rooms at a hospital in Wuhan and the patient room within another “had an undetectable SARS-Cov-2 concentration in the air.”

WHO reaffirms its position

Even so, the WHO insists that there is insufficient evidence to demonstrate that COVID-19 is transmissible as a pathogen in the air. In fact, the organization has questioned the US study, stating that the experiment used "a high-powered machine that does not reflect normal human cough conditions". In addition, although this study pointed to the appearance of the coronavirus in aerosol particles for up to three hours, it does not reflect a clinical environment where aerosols are produced, says WHO.

The Centers for Disease Control and Prevention have also noted that "the contribution of small respirable particles, sometimes called aerosols or drop cores, to proximity transmission is currently uncertain".

The WHO reiterates the vital recommendations for the general population to wash their hands frequently, to cough on their elbows, not to touch their eyes, nose or mouth, to routinely disinfect the environment, maintain a minimum distance of one metre from other persons and avoid unprotected contact with persons with fever or other respiratory symptoms.

Not everyone agrees

A prestigious scientific panel told the White House earlier this week that research shows that the coronavirus could be transmitted not only by sneezing or coughing, but also by speaking or even breathing.

"While current specific research on the coronavirus is limited, the results of available studies are consistent with the aerosolization of the virus by normal breathing,” according to the letter, written by Dr. Harvey Fineberg, Chairman of a committee of the National Academy of Sciences.

When public health officials say that there is not enough evidence to say that COVID-19 spreads through the air, they refer specifically to being transported in aerosols loaded with viruses less than five micrometres in diameter. Compared to drops, aerosols can stay in the air longer and travel much longer.

Most of the transmission occurs at close range, according to Nature Ben Cowling, an epidemiologist at the University of Hong Kong. However, the distinction between drops and aerosols is not useful because “particles that come out with the virus can have a wide range of sizes,” he says. And if SARS-Cov-2 is transmitted in aerosols, virus particles may accumulate over time in enclosed spaces or be transmitted over long distances.

Shall we wear masks?

Experts say that there is no need to wear surgical masks, as long as a screen is used to prevent the spread of the infection, it is enough. A cloth mask, a handkerchief, a ski mask, a scarf...

According to the US Centers for Disease Control and Prevention. In the United States, the virus is transmitted from person to person when individuals are about two metres away from each other "through the breathing drops produced when an infected person coughs or sneezes".

How long the coronavirus stays in the air depends on several factors, including the amount of virus that an infected individual emits when breathing or speaking, and also the amount of circulation in the air, according to the expert.