What if Covid-19 is transmitted by air?

How significant is airborne transmission of the virus which causes Covid-19? This question has bothered scientists, health workers and the public since the global outbreak began in January 2020.

The debate on airborne transmission of Covid-19 intensified in early July as 239 scientists from 32 countries issued an open “appeal to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of Covid-19.”

A few days later, the World Health Organization (WHO) updated its 29 March scientific brief entitled “Modes of transmission of virus causing Covid-19: implications for infection prevention and control (IPC) precaution recommendations”. This debate is not just a storm in a scientific teacup. It has very important policy implications for infection and protection measures, including those to safeguard health workers’ safety and health.

In practical terms for health workers, this would entail the use of personal protective equipment, including respirators in preference to medical masks.

The first WHO guidance on the disease was the “Infection prevention and control during health care when novel coronavirus (‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎nCoV)‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎ infection is suspected” document issued on 25 January. It was adapted from earlier infection prevention and control (IPC) guidance developed to address the Middle East respiratory disease syndrome coronavirus (MERS-CoV) infection. It placed emphasis on contact and droplet precautions.

An open letter was immediately issued by Global Nurses United, signed by nurses’ unions, including PSI affiliates. The letter pointed out that the guidance fell short of what was required to protect the lives of nurses and other health workers. Considering the fact that much remained unknown about the virus and its modes of transmission, they called for “airborne precautions to be implemented when healthcare workers are caring for patients with possible or known 2019-nCoV infections.”

This would be in line with the precautionary principle “which states that we should not wait until we know for certain that something is harmful before we take action to protect people’s health.” In practical terms for health workers, this would entail guidance calling for all health workers caring for confirmed or suspected COVID-19 cases to use personal protective equipment, including respirators in preference to medical masks.

Until now, WHO guidance documents have stressed that respirators need to be used only where health workers carry out aerosol-generating procedures. These are medical procedures which “can produce very small droplets (called aerosolized droplet nuclei or aerosols) that are able to stay suspended in the air for longer periods of time.” These aerosols can contain the coronavirus.

Key Figures

According to John Hopkins University - as of 10 July 2020 (worldwide)







Behind the assertion of the over 200 experts that “it is time to address airborne transmission of Covid-19”, lies the fact that studies they and other scientists have conducted “demonstrated beyond any reasonable doubt” that viruses are released as when infected persons exhale, cough or talk, in “microdroplets small enough to remain aloft in air”. This, as they further point out; “poses a risk of exposure at distances beyond 1-2m from an infected individual”.

WHO says more information is needed to better understand Covid-19 transmission, since it is a new disease. And there have been instances where WHO officials have had to backtrack on responses during question and answer sessions, for example in June concerning transmission by asymptomatic infected persons.

Within this context and putting the unacceptably high rate of infection among healthcare workers in perspective, we are strongly of the view that a precautionary approach should be palpable in WHO’s IPC guideline. For example, health workers’ unions are convinced that the use of respirators and not medical masks should be explicitly recommended for healthcare workers taking care of all suspected or confirmed cases of Covid-19 and not only when carrying out aerosol-generating procedures.

In its 5 June recommendation on masks, the WHO pointed out that “availability of medical masks versus respirators, cost and procurement implications, feasibility, equity of access to these respiratory protections by health workers around the world” were part of the considerations behind sticking with earlier recommendations on using medical masks rather than respirators for most health workers.

These are issues that go beyond the science. And they are not natural, they spring out of the commodification of social life that has become the norm, allowing corporations’ wealth to be prioritized over people’s health. The global emergency has to be addressed with rapid changes that unapologetically put people over profit, as we stated in the PSI priorities and perspective.

When it comes to waging wars and repressing citizens, for most governments there is hardly ever a lack of availability of arms and ammunitions. Why is a shortage of necessary PPE such as respirators still the norm six months into the pandemic?

Covid-19 might not be going away as soon as we would hope. And there is indeed need for more information to better understand this disease and how it is transmitted. But with mounting evidence that its transmission could be airborne, many lives – particularly of health workers – could be saved if the precautionary principle is applied.

With its global norm setting role, we urge WHO to take steps in this direction. PSI and its affiliates will also campaign for national bodies to take measures that better safeguard the lives of our members and the public at large.