With all medical and social measures primed and ready, the hope is that we may avoid a second wave of viral attack.

The experience of South Korea and Hong Kong shows that with one false move, the coronavirus rears its head with a vengeance (Singapore must be ready to face second Covid-19 wave: Gan, July 18).

All it takes is careless cross-border control, indulgent revelry, irresponsible merrymaking or people adopting questionable mask apparel for the virus to expose the chink in our armour.

Of late, I have seen more and more people take to wearing masks with valves that tout the added advantage of increasing airflow during exhalation for wearers.

These are useless for keeping viruses in for carriers of the coronavirus. In other words, people should not be allowed to wear them.

Yik Keng Yeong (Dr)