LONDON • When I got off my flight from Beijing to London nearly two weeks ago, I knew what I had to do: go straight into self-quarantine.

I live in China, where a dramatic lockdown since late January has made it clear that all residents, even those well beyond the epicentre's outbreak in Wuhan, were in the middle of a global health crisis. The boarding process in Beijing was the final reminder: two mandatory temperature checks and an electronic health statement for which I had to provide an e-mail address and two contact phone numbers.