The mask part actually has nothing to do with COVID-19, it was given to Earth in the LN too, and that was published way back in 2015. Though it IS a very convenient coincidence, a coincidence it is nonetheless.
It's just the Japanese love their masks, many people wear them there just for anonimity, others to reduce the effects of hay fever etc. It's more of a fashion accessory there. Sorry for the late reply, I just wanted to check the LN.