Submarines, Usually an Ideal Place for Disease to Spread, Manage to Keep COVID-19 at Bay

I have a strong suspicion masks are key to protecting from COVID-19. Japan's high density population of 110 million in a small country requires several million to ride trains and subways every day, but its total cases is less than 50,000. Millions are subject to closed environments and close proximity to others, but their case count is significantly low.

keep 'em clean