EARLIER THIS week, the office of the Principal Scientific Adviser to the government issued a detailed manual on how to make home-made masks and recommended it to everyone, especially those living in densely populated areas, to protect themselves from novel coronavirus disease. This was the first time that masks were being officially recommended for everyone, even for those who were not infected or were not in close contact with anyone infected.
The Ministry of Health and Family Welfare had earlier said that everyone “need not” wear masks. That instruction still stands. The World Health Organization (WHO) has a similar standing recommendation, that non-infected persons should wear masks only if they are caring for sick ones. The US Centers for Disease Control and Prevention (CDC) has the same recommendation, though it is being reconsidered now.
How do masks help?
By covering the nose and mouth, masks reduce the possibility of the virus getting inside the respiratory tract. SARS-CoV2, the virus behind COVID-19 disease, is being transmitted through air droplets that are released, for example, when an infected person coughs. Recent research published in the New England Journal of Medicine said the virus could remain in the air for up to three hours. The virus is also known to survive on plastic, steel and copper surfaces for several hours, and there is a risk in people touching these surfaces and then touching their mouth or nose. A mask can be handy in these kind of circumstances as well.
The virus is also being spread by asymptomatic patients. As such, in public places, one cannot be sure whether an infected person is in close proximity or not.
So, what explains the previous advice against wearing masks?
The main reason is to ensure that there is no run on the professional quality masks that are needed by healthcare professionals, who are at maximum risk because of their proximity to infected patients. As it is, there is a severe shortage of professional masks globally, because of the huge demand.
The advice had come at a time when the virus was not known to stay in the air for any significant amount of time. It was only in March that research was published showing that the novel coronavirus can indeed survive in the air for up to three hours. Until then, only patients, especially those who were prone to coughing, and those caring for a patient, like family members or healthcare professionals, were advised to wear masks. The general public was discouraged from wearing them. Now, the latest research is forcing a rethink.
How effective are professional masks?
The one in great demand is called N95, so named because it is able to block at least 95% of particles in the air that are of the size 0.3 microns or bigger (1 micron is a millionth of a metre). A single SARS-CoV2 virus is typically up to 0.2 microns in size, so it can possibly penetrate the N95 mask. But as Arnab Bhattacharya, a professor and Chair of Public Outreach at the Tata Institute of Fundamental Research in Mumbai, points out, the virus is enclosed in air droplets that are much bigger in size. “What is getting spread are droplets, which are a few microns in size. Though there is a size distribution, it is very unlikely that there are droplets that are less than 0.3 microns in size. So that way the N95 is a very good barrier to virus entry,” he says.
Bhattacharya said N95s are much better than the typical surgical masks worn by medical staff whose main purpose is to keep out large droplets of wearer’s saliva from going out, for example during a surgery.
What about home-made masks?
Home-made masks might not be as effective in blocking outside particles as professional masks, but they are nonetheless better than not having a mask at all. Simple masks made of cotton cloth do keep out larger particles. And these can be washed and reused multiple times.
So what is the latest recommendation?
The manual issued by the office of the Principal Scientific Adviser strongly recommends that people wear home-made masks, though it does point out that this might not be sufficient. “Masks are effective only when used in combination with frequent hand-cleaning with alcohol-based hand rub or soap and water,” it says, quoting the WHO. It says use of clean masks “will be vital” to stopping the spread of the virus, and adds that these were “especially recommended for people living in densely populated areas across India”.
The manual says a home-made double-layered mask made of 100 per cent cotton cloth was 70 per cent as effective as a surgical mask in blocking small particles, even those that are five times smaller than the novel coronavirus.
While the general advisories of the Health Ministry and the WHO remain unchanged, the CDC in the US was expected to advise all Americans to start wearing cloth masks in public spaces, according a report in The New York Times on Friday.
Here’s a quick Coronavirus guide from Express Explained to keep you updated: What can cause a COVID-19 patient to relapse after recovery? | COVID-19 lockdown has cleaned up the air, but this may not be good news. Here’s why | Can alternative medicine work against the coronavirus? | A five-minute test for COVID-19 has been readied, India may get it too | How India is building up defence during lockdown | Why only a fraction of those with coronavirus suffer acutely | How do healthcare workers protect themselves from getting infected? | What does it take to set up isolation wards?
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