Ebolavirus comes in six varieties: Zaire, Bundibugyo, Sudan, Tai Forest, Reston, and Bombali. The Zaire ebolavirus was responsible for the most recent Ebola epidemics in West Africa (2014–2016) and the Democratic Republic of the Congo (2018–2019). It is a large virus, about 30 nanometers in diameter, with a single-stranded RNA genome that contains three genes coding for the viral proteins VP24, VP40, and NP. It is believed that when infected by this virus, people become immune to further infections by the same species of virus. However, there is no evidence that would indicate that someone who has been infected with one variety of Ebolavirus can be infected with another variety later in life. Although there have been reports of people who have survived ebolavirus infections, it is not known how many years ago they were infected or what kind of virus they had originally. It is possible that both viruses share some similarities in their structure that allows the person's body to respond accordingly, however, this idea has yet to be confirmed by scientific studies. In addition to human beings, other animals have been found to be infected with ebolaviruses including monkeys, apes, and several species of bats. Ebola virus is named after the country where it was first discovered - Zaire.