New Delhi: A cloth mask protects not just other people but also the wearer from the SARS-CoV-2 virus, according to the US Centres for Disease Control (CDC).
In a new brief issued Tuesday, the CDC recommended wearing non-valved multi-layer cloth masks to prevent transmission of Covid-19. It noted that masks prevent transmission of the virus by pre-symptomatic and asymptomatic individuals and also helps reduce inhalation of these droplets by the wearer.
“The community benefit of masking for SARS-CoV-2 control is due to the combination of these effects; individual prevention benefit increases with increasing numbers of people using masks consistently and correctly,” the CDC said in a statement.
This is a move away from the body’s earlier stand that masks are intended to reduce the emission of virus-laden droplets only from infected wearers who may be asymptomatic.
The SARS-CoV-2 virus is transmitted predominately by respiratory droplets generated when people cough, sneeze, sing, talk or breathe.
According to the CDC, cloth masks not only effectively block most large droplets, but can also block the exhalation of fine aerosols. Multi-layer cloth masks can block up to 50-70 per cent of aerosols and also limits the forward spread of those that are not captured.
In its statement, the US health body cited several studies to note that more than 80 per cent of all respiratory droplets were blocked with cloth masks. In some studies, the cloth masks performed on par with surgical masks.
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‘Universal masking may avert future lockdowns’
While the effectiveness of various masks has varied widely across studies, multiple layers of cloth with higher thread counts have demonstrated superior performance compared to a single layer of cloth with lower thread counts.
Some materials like polypropylene may enhance filtering effectiveness by generating a form of static electricity, while silk may help repel moisture droplets — maintaining breathability and comfort, noted the CDC.
The statement also referred to a study of a high-exposure event, where 2 Covid-19 positive hair stylists interacted for an average of 15 minutes with about 139 clients during an eight-day period. However, none of the 67 clients, who subsequently consented to an interview and testing, were infected.
The stylists and clients universally wore masks in the salon as required by local ordinance and company policy at the time.
In another study of 124 households in Beijing with less than one case of Covid-19, mask use by the patient and family contacts before the patient developed symptoms reduced secondary transmission within the households by 79 per cent.
“Adopting universal masking policies can help avert future lockdowns, especially if combined with other non-pharmaceutical interventions such as social distancing, hand hygiene, and adequate ventilation,” CDC said in its statement.
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