Even a simple surgical mask can prevent spread of Covid, German study says

In environments with potentially high airborne virus concentrations such as medical settings & densely occupied indoor spaces, masks with higher filtration efficiency should be used.

Surgical masks (representational image)| Photo: Pixabay

New Delhi: A simple surgical mask effectively reduces the transmission of the novel coronavirus in most environments and situations, according to a new study from Germany.

However, in environments with potentially high airborne virus concentrations such as medical settings and densely occupied indoor spaces, masks with higher filtration efficiency, such as the N95 masks, should be used and combined with other protective measures such as intensive ventilation, said the study.

Published in the journal Science, the study used observational data and model calculations to answer questions about which masks work under what circumstance.

“For the airborne transmission of SARS-CoV-2, we find that usually just a minor fraction of exhaled respiratory particles contains viruses. Most environments and contacts are under virus-limited conditions, where face masks, including simple surgical masks, have a high efficacy in preventing the spread of Covid-19,” Yafang Cheng, one of the authors who is from the Max Planck Institute for Chemistry in Germany, said in a statement.

“Our study provides a detailed and novel mechanistic understanding of population-average mask efficacy, which explains why regions with a higher percentage of the population wearing masks have better control of the pandemic,” Cheng said.

However, in virus-rich indoor environments with high infection probability, more advanced masks — such as the N95 or the FFP2 — and other protective equipment are required to prevent airborne transmission.

“The combination of high-efficiency masks with other protective measures is particularly important for hospitals, medical centers, and other indoor environments, where high risk patients may encounter high virus concentrations,” said Christian Witt, one of the authors of the study, from the Charité-Universitätsmedizin Berlin.

“Masks will remain an important protective measure against SARS-CoV-2 infection — even for vaccinated persons, especially when the protection provided by vaccination decreases over time,” Witt added.

What the study says on compliance

The methods used in the study can also be used to assess the efficacy of masks and other preventive measures against emerging variants of SARS-CoV-2, the researchers said.

The study also showed how important it is for people to use masks correctly and widely to lower the spread of the disease.

For the effective reproduction number (R) — a key measure of how fast the infection is spreading — to drop below 1, at least 60 to 70 per cent of the population needs to follow the masking protocol, the study noted.

This compliance percentage falls to about 40 per cent if the population uses N95 or FFP2 masks.

The rates of compliance would be required for more infectious variants of SARS-CoV-2, the study said.

“Our study explains quantitatively why and how face masks are highly effective in virus-limited environments and less effective in virus-rich environments — both at the individual and the population average level related to observed infection rates and effective reproduction numbers,” said Ulrich Pöschl, director of the Multiphase Chemistry Department at the Max Planck Institute for Chemistry.

“This has not been achieved before and is essential to overcome inconclusive earlier results, arguments, and discussions,” Pöschl added.