For yet another week, covid-19, the disease caused by the new coronavirus, has remained poised just short of becoming a pandemic. As case counts stabilise in China, and don’t take off elsewhere, the big question is: will it happen? “Every scenario is still on the table,” said Tedros Ghebreyesus, head of the World Health Organization (WHO), in Geneva, Switzerland, this week.
To be pandemic, covid-19 has to spread generally in a population outside China, not just in limited clusters triggered by …