Emerging and Reemerging Viral Diseases

An emerging infectious disease (EID) is defined as a disease caused by a pathogen that has not been observed previously within a population or geographic location. Viruses are a major cause of EIDs, particularly −ssRNA viruses. Many variables are involved in the emergence or reemergence of viruses. These can be classified into human factors, environmental/ecological factors, and viral factors and include urbanization, globalization, weather and climate change, and the genetic composition of the virus. The great majority of emerging viral diseases are zoonoses, notably transmitted by arthropods and nonhuman mammals. Flaviviruses include several notable vector-transmitted viruses, while rodents and bats are thought to be the natural reservoirs of arenaviruses and filoviruses, respectively. This chapter discusses several notable outbreaks of emerging and reemerging viruses, including the 2014–15 outbreak of Ebolavirus in West Africa.