That question turns out to be difficult to answer. A recent scientific publication concludes that masks are the most important way to prevent spread. That led to a lot of criticism.
Wearing masks is “the most effective way to prevent virus transmission between humans,” the researchers write in the scientific journal PNAS. “Combined with keeping a meter and a half away, washing hands, quarantine in case of illness and contact investigation, it is our best chance to stay on top of the virus as long as there are no drugs or vaccines.”
The researchers did not study the effect of masks or how the virus can spread through the air. They relied on information about the numbers of infections in certain areas and the mandatory measures taken there.
Importance of a mask
The study, led by Renyi Zhang of Texas A&M University, looked at the COVID-19 outbreaks in China, Northern Italy, and New York between January 23 and May 9. In the beginning, there was a steady increase in the number of infections worldwide, and in China, Northern Italy, and New York. According to the researchers, the number of infections leveled off as soon as the wearing of mouth masks became mandatory.
In China, compulsory face covering was immediately part of the preventive measures. In New York and Northern Italy, only other measures were taken at first, such as washing hands, keeping your distance, quarantine, and isolation in case of symptoms. After a month, mouth masks became mandatory. According to the researchers, the number of infections only leveled off as soon as the masking obligation was added.
Therefore, they conclude that the first measures were not enough to prevent the virus from spreading via small, virus-carrying droplets in the air. They, therefore, consider masks an essential part of prevention.
This conclusion has been picked up by various media outlets, causing concern among other researchers. A group of US scientists wrote an open letter to PNAS requesting that the article be withdrawn. “While we agree that face masks play an important role in slowing the spread of COVID-19, the claims made in this study were based on false assumptions and methodological errors,” the critics write.
An example is the PNAS article’s assumption that since April 3, the only difference in measures between New York and the rest of the United States is the mask requirement, which was introduced in New York on April 17. The critics refute this: “It is plainly incorrect that there were no other regulatory differences between New York and the rest of the US on those dates. Nor is it true that New York was the only region in the US to mandate facial covers. “
Furthermore, the letter writers disagree with substantiating that air transmission is the dominant route for COVID-19 spread. The researchers conclude this because “worldwide distance, quarantine, and isolation is mandatory since the beginning of April,” while the infections steadily increased during that period. But, the critics refute, “by April many regions (e.g., Sweden, parts of the United States) were not closed off, and quarantine and isolation were not applicable in most parts of the world
Mask or no mask?
The PNAS article was therefore not scientifically substantiated, but what does that mean for the masks? Other (pre) publications also show a connection between the obligation to mask the mouth and decrease the number of infections. This has been reported, for example, for the German city of Jena.
For these studies, it has not been directly investigated how mouth masks would reduce infections. In de Volkskrant, infectious disease modeler Luc Coffeng said about this: “It is quite easy to imagine that the obligation in itself has an effect. Mandatory masks can send a signal to citizens that they really mean business. So citizens are going to wear masks, but also behave more carefully. “
Yet there is also something to be said from virology for the use of masks, says medical virologist Mariet Feltkamp, of the Leiden University Medical Center (LUMC). “A study from the beginning of April shows that small exhaled aerosols (small, floating droplets — ed.) Can contain coronavirus and that they are caught by a mouth mask. This study was done with a different coronavirus, but I see no reason why this should not hold true for the current SARS-CoV-2. “
Guidelines and advice
In early June, the World Health Organization (WHO) released new guidelines on mouth masks about COVID-19, following recent studies. The organization recommends use where sufficient distance is not possible, such as in public transport, in shops, or in other closed or busy environments. The WHO also recommends using risk groups and all healthcare workers, including those who do not work directly with COVID patients.
The WHO does emphasize that masks are only “part of a comprehensive strategy in the fight against COVID.” “Face masks alone don’t protect you against COVID-19.”.”