Covid-19: humidity inside masks is a good thing

We know that wearing a mask reduces the risk of transmission of the coronavirus because it blocks aerosols dispersed by talking or coughing. But a new study from the National Institute of Health (NIH) of the United States indicates that the mask has a double interest for the person wearing it. Indeed, when we breathe, a certain humidity is formed inside the mask. And “the effective humidity of the inhaled air, promotes hydration of the respiratory epithelium, which is beneficial for the immune system” underline the researchers from the NIH National Institute of Diabetes and Digestive and Kidney Diseases, in their study published in the Biophysical Journal.

“High levels of humidity have been shown to attenuate the severity of influenza and this may apply to the severity of Covid-19 through a similar mechanism,” they add. High levels of humidity can indeed limit the spread of a virus to the lungs by promoting mucociliary clearance (MCC), a defense mechanism that removes mucus and potentially harmful particles in the mucus from the lungs. A high level of humidity in the inhaled air also strengthens the immune system by producing proteins called interferons, which fight against viruses.

Masks block 99.9% of large droplets

Respiratory droplets are the main route of transmission for the coronavirus. These droplets are either inhaled or deposited on the recipient’s mouth or conjunctiva, or deposited on a surface and then transmitted mechanically through physical contact. And the larger the droplets (like the postilions) the more they disperse the virus. A new study from the University of Edinburgh (Scotland) shows that wearing a mask helps block 99.9% of these large droplets that we project when we cough, sneeze or speak loudly.

“For this study, we did a test with a mannequin head that ejected fluorescent water droplets under normal speech and cough conditions, facing people placed 2 m away without a face mask, with a surgical mask or a single-ply cotton face covering. We quantified the number of airborne droplets using laser imaging and UV light imaging.” Ignazio Maria Viola, principal author of this study.

“We have estimated that a person standing 2m away from a coughing person without a mask is exposed to more than 10,000 times more respiratory droplets than a person standing 0.5m away wearing a single layer mask of In our study, for the largest droplets that we measure, we’re talking about 99.9% reduction.”

If 7 out of 10 people wore a mask, the virus would be stopped

“Surgical masks have an estimated effectiveness of around 70%, if at least 70% of people used these masks in public consistently, this could lead to the eradication of the Covid-19 pandemic” say the researchers of the University of Singapore.

In a study on the diffusion of respiratory droplets from people with Covid-19, published in the journal Physics of fluid, researchers say that the key measure to fight against the coronavirus is none other than wearing a protective mask. And after analyzing the size of the respiratory droplets that spread the virus, they indicate that FFP2 masks are the only ones really capable of filtering aerosol-sized droplets.

The WHO also recommends the mask … but not the visors

For its part, the World Health Organization has just updated for the fourth time its recommendations on wearing a mask. Since December 2, the world organization “advises the general public to wear a non-medical mask indoors (for example in shops, shared workplaces, schools) or outdoors, when a distance physical height of at least one meter cannot be maintained”.

However, the WHO recommends not to use a mask with valves or transparent visors, which provide much less protection than conventional masks. It also advises against wearing a mask during intense physical activity.

To reduce your risk from #COVID19, #WearAMask when you are spending time indoors with people who are not part of your household unless you’re sure the ventilation is good ⬇ pic.twitter.com/YYfiqk9bTZ

— World Health Organization (WHO) (@WHO) December 2, 2020