Spillover: Animal Infections and the Next Human Pandemic

by David Quammen

conditions while the primary mission was not science but saving lives, even the experts aren’t sure exactly how the virus typically causes death. “We don’t know the mechanism,” Pierre Rollin told me. He could point to liver failure, to kidney failure, to breathing difficulties, to diarrhea, and in the end it often seemed that multiple causes were converging in an unstoppable cascade. Karl Johnson voiced similar uncertainty, but mentioned that the virus “really goes after the immune system,” shutting down production of interferon, a class of proteins essential to immune response, so that “nothing stops the continued replication of the virus.” This idea of immune suppression by ebolaviruses has also appeared lately in the literature, along with speculation that it might allow catastrophic overgrowth of a patient’s natural populations of bacteria, normally resident in the gut and elsewhere, as well as unhindered replication of the virus itself.