Scientists ask if Ebola immunises as well as kills

A recent sharp drop in new Ebola infections in West Africa is prompting scientists to wonder whether the virus may be silently immunising some people at the same time as brutally killing their neighbours. So-called “asymptomatic” Ebola cases – in which someone is exposed to the virus, develops antibodies, but doesn’t get sick or suffer symptoms – are hotly disputed among scientists, with some saying their existence is little more than a pipe dream. Yet if, as some studies suggest, such cases do occur in epidemics of the deadly disease, they may be a key factor in ending outbreaks more swiftly by giving secret protection to those lucky enough to be able to bat the infection away. “We wonder whether ‘herd immunity’ is secretly coming up – when you get a critical mass of people who are protected, because if they are asymptomatic they are then immune,” Philippe Maughan, senior operations administrator for...