![Medical imaging is being used to work out how the coronavirus affects the body](http://healthek.eu/wp-content/uploads/2020/02/pa-50385449.jpg)
Feng Dapeng/Xinhua News Agency/PA Images
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 …