That every individual wears a mask in public is the first line of defense to cut the transmission channels for the novel coronavirus. The importance of wearing a face mask can never be overemphasized.

That explains why the National Health Commission has released new guidelines for wearing masks, which specify what kind of masks should be worn by those in higher-risk places and how ordinary residents should wear a mask.

Different from before, besides the mandatory requirement of wearing masks in enclosed venues, the latest guidelines require ordinary residents to wear a mask even in open spaces if there is a gathering. This is because the virus is constantly mutating and the Delta variant is much more transmissible than previous strains. It is quite likely that any mutation of the Delta variant will be even more transmissible and pose an even greater threat to public health.

That the wave of Delta cases has caught many countries off guard should serve as a reminder to China that its vigilance against the virus cannot be slackened.

The story of an old lady is a case in point to testify how effective masks can be in protecting people from being infected. This lady was infected and traveled from Nanjing, capital of East China's Jiangsu province, to Yangzhou, another city in the province. Although she passed the virus to many players at a mahjong parlor where the majority of those present did not wear masks, she did not pass the virus to anyone during her journey because all the passengers on her train and then the bus she took were wearing a mask.

The number of domestic cases detected has been on the decline since July 20 when this wave of Delta cases was first identified in Nanjing. The total number of local cases reported on Sunday was 24, and only in Jiangsu, Henan and Hunan provinces.

Hopefully, there will be no cases reported in those three provinces in a couple of weeks. Life and work in those districts which have been designated as high- and medium-level risk areas will then return to normal.

It should still be mandatory for residents to wear a mask in enclosed spaces and at open gatherings. People should err on the side of caution when the pandemic is still raging in many parts of the world and cases as well as asymptomatic carriers from abroad are reported on a daily basis.

Those working at customs or ports where the chance of being infected by someone carrying the virus from abroad or even from cargoes carrying the virus should strictly follow the rules and wear higher-level protection masks. As long as all follow the rules and wear masks as required, the country will be able to control the virus.