Rockefeller University's Jean-Laurent Casanova has dubbed this "the infection enigma," it adds. He notes that there are number of instances in which some people become gravely ill from infections that others have a mild case of. For instance, he says that some people develop encephalitis from herpes simplex virus infections, while others develop cold sores or genital lesions and, similarly, Candida albicans usually only causes problems in people with weakened immune systems, but occasionally leads to infections in seemingly healthy people.
As Scientific American writes, Casanova has pinpointed gene mutations affecting interferons that could affect people's abilities to fight off infections as well as mutations linked to increased tuberculosis susceptibility. This could mean, it says, that some patients with severe infections and their families could benefit from genetic screening.