With the emergence of more infectious coronavirus variants, coupled with the rise in the number of Covid-19 cases in Singapore, experts are warning of the possibility of a spike in infections ahead.

This underlines the importance of proper mask wearing, especially when entering crowded places, and ensuring that one’s mask offers good protection against possible infection, they said.

Infectious diseases expert Leong Hoe Nam said there is a “real risk” of transmission rates going up during the Chinese New Year period due to the potential for increased socialising, along with the recent rise in imported cases.

“We must remember that the polymerase chain reaction test is only 93 per cent sensitive, which means that for every 40 positive imported cases, there will be one or two cases that we miss out on, which may end up seeping into the community,” he said.

This may result in an increase in community cases, to which our next level of defence would be masks, making it important to choose an effective one, he added.

For a mask to be effective, it should have three layers, with a non-woven fabric in the middle to absorb particles and a water-repellent outer layer, said Dr Teo Tee Hui, council member at the Institution of Engineers, Singapore.

Examples of these include surgical masks and the antimicrobial 3D masks given out by Temasek Foundation in the latest distribution drive, which began on Nov 30.

Professor Teo Yik Ying, dean of the Saw Swee Hock School of Public Health at the National University of Singapore (NUS), said there is “no evidence” suggesting that surgical masks or N95 masks are necessary for protection against new variants of the virus, such as the N501 strain identified in South Africa and the B117 strain in the UK. There were three linked cases of the latter in the community here recently.

“Although some of the new variants may have been associated with droplets presenting a higher viral load, face masks that were previously effective in containing the projection of droplets (from an individual) will still remain effective,” he said.

“Therefore, if one is already using a triple-layered reusable face mask, it will still be sufficient to protect against new variants, especially since the transmission mechanism of the Sars-CoV-2 virus remains the same.”

(Read also “Should I Wear A Face Mask Or Face Shield When I Go Out?“)

Face masks which are single-layered or poorly constructed would have provided much lower protection even before the emergence of the variants, and would continue to do so, he added.

His colleague, Professor Hsu Li Yang, programme leader of infectious diseases and vice-dean for global health at the NUS Saw Swee Hock School of Public Health, noted that the UK and South Africa variants of the virus appear to be “more efficient at attaching to and invading human cells”, which means a smaller “dose” of the virus could result in infection.

“In response, several European countries have indeed recommended that medical-grade masks – which include surgical masks – be used in all public places,” he said.

In Germany, for instance, it was mandated that people must wear surgical masks or masks of higher specifications, such as N95 masks, in shops and public transport as part of measures to control the faster-spreading strains of the coronavirus.

But Prof Hsu noted that the World Health Organisation has not changed its stance to recommend triple-layered masks in the community as yet, though he acknowledged that those who wear single or double-layered cloth masks could be at greater risk of being infected when exposed to new strains of the virus.

He said masks on their own do not offer total protection against infection, but wearing one works in tandem with preventive measures such as physical distancing and hand-washing.

Experts have also cautioned that it is not just about the type of face masks that are worn, but also the way in which they are worn.

Dr Leong said it is important to select a mask that fits well so that little unfiltered air leaks in.

A good way to check would be to breathe through the mask and ensure that air is not flowing in from either side or the top and bottom of the mask, he added.

Different types of masks

This article was first published in The Straits Times.