THE new coronavirus has already infected millions of people, but we are still learning about who is most vulnerable to its attacks. It quickly became clear that older people and those with certain underlying health conditions such as diabetes and cancer were at higher risk. But there have now also been many reports of the disease killing young, otherwise healthy individuals. And even among the high-risk groups, the threat that covid-19 poses varies dramatically. What’s more, information from several countries now indicates that people from some ethnic minorities are more likely to die. So are men and people who are obese.