Corona virus| The ultimate covid-19 mystery: Why does it spare some and kill others?
The novel coronavirus can be a killer — or no big deal. It can put a person in the intensive care unit on a ventilator, isolated from family, facing a lonely death — or it can come and go without leaving a mark, a ghost pathogen, more rumor than reality. Six months into a pandemic that has killed more than 400,000 people globally, scientists are still trying to understand the wildly variable nature of covid-19, the disease caused by the virus. Among their lines of inquiry: Are distinct strains of the coronavirus more dangerous? Does a patient’s blood type affect the severity of the illness? Do other genetic factors play a role? Are some people partially protected from covid-19 because they’ve had recent exposure to other coronaviruses? Much of the research remains provisional or ambiguous, and for now scientists can’t do much better than say that covid-19 is more likely to be worse for older people — often described as over the age of 60 — and for those with chronic conditions suc...