Ebola and Marburg are among the most deadly viruses, with mortality rates from these infections ranging from 25% to 90%. While no drugs currently are available on the market to prevent infection from these viruses—they belong to a category of viruses called filoviruses, which are known to cause hemorrhagic fever—researchers have identified a few small drug molecules that can block filoviruses from infecting cells by occupying a single site on a glycoprotein in the virus.