My laboratory’s current focus is the understanding of what make some viruses highly pathogenic, whereas other very closely related viruses will cause no disease in humans or animals. The viruses we are utilizing for this work are the henipaviruses and the filoviruses, with both of these groups of viruses containing viruses that result in lethal infections (case fatality rates of greater than 70%) and other closely related viruses that don’t cause disease in humans and animals. Both of these viruses require biosafety level 4 containment, the highest level of biocontainment. Using reverse genetics and animal infection models we are investigating the molecular basis of these extreme differences. A greater understanding of these molecular determinants of pathogenicity will lead to improved risk management of newly discovered or newly emerging viruses and development of improved vaccines and therapeutics.