Proof that face masks reduce SARS-CoV-2 transmission
Researchers in Germany and China conducted a study analyzing the effectiveness of face masks in reducing the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the causative agent of coronavirus disease 2019 (COVID-19) has been.
Hang Su from the Max Planck Institute for Chemistry in Mainz and colleagues showed that differences in the effectiveness of wearing a mask are due to different SARS-CoV-2 frequencies and can be related to the population average probability of infection.
The team found that the frequency of the virus is low in most environments, which means surgical masks would be effective in preventing transmission.
However, in potentially virus-rich indoor spaces like hospitals and medical centers, more advanced masks and other protective equipment would be required to prevent transmission, according to Su and colleagues.
In the journal Science *, the researchers also write that masks are particularly effective when used in combination with other preventive measures such as ventilation and social distancing.
The effectiveness of face masks is still being debated
Airborne transmission is one of the main ways SARS-CoV-2 is spread, and wearing face masks was widely advocated during the COVID-19 pandemic.
However, the effectiveness of wearing masks is a topic of debate as, for example, surgical masks have been shown to have variable penetration rates ranging between 30% and 70%.
In addition, randomized clinical trials have produced inconsistent or inconclusive results, with some reporting only marginal benefits from mask use. However, observational studies have shown that transmission was better controlled in environments where a high proportion of people wore masks.
What did the researchers do?
Su and colleagues developed a quantitative model of airborne virus exposure that they used to determine the effectiveness of face masks.
The team showed that the effectiveness of face masks varied depending on the frequency of the virus in the air.
Based on measurements of SARS-CoV-2 in air samples and population-level infection probabilities, the researchers found that the virus frequency in most environments is low enough for masks to be effective in reducing airborne transmission.
Calculating the impact of wearing a mask on the likelihood of infection
Using a single-hit infection model, Su and colleagues found that in a virus-rich environment, the likelihood of infection is not sensitive to changes in the total number of viruses, and wearing masks may not be enough to prevent infection.
In a virus-limited environment, however, the likelihood of infection is very sensitive to fluctuations in the total number of viruses and is significantly reduced by wearing masks.
“Therefore, we need to determine the airborne virus frequency regime to understand the effectiveness of the mask,” say the researchers.
Next, the team compared the effectiveness of surgical masks and N95 masks between virus-limited and virus-rich states.
This showed that under virus-limited conditions, the masks reduced the likelihood of infection by as much as their filtering efficiency, but that they were much less effective in the virus-rich regime.
“Accordingly, experimental studies can determine poor mask effectiveness when carried out under virus-rich conditions,” write Su and colleagues.
The results also suggest that potentially virus-rich indoor spaces such as medical centers and hospitals require more advanced masks and other protective equipment.
Synergistic effects of combining mask wear with other measures
The team says that the increasing effectiveness of mask use in low-virus conditions indicates the possible synergistic effects of combining masks with other measures to reduce airborne frequency, such as: B. Ventilation and social distancing.
The researchers found that the use of ventilation changed an environment from virus-rich to virus-limited, which has a significant impact on medical centers with relatively high SARS-CoV-2 incidence. In addition, the use of ventilation increased the effectiveness of face masks in virus-rich environments and the effectiveness of social distancing.
“The more measures are applied, the more effective each measure will contain the virus transmission,” says Su and colleagues.
The researchers say that proper ventilation and social distancing will decrease virus levels in the area and increase the effectiveness of face masks in curbing transmission.
“In addition, high compliance and the correct use of masks are important to ensure the effectiveness of the universal masking,” the team concludes.