It is recommended that survivors of EVD wear condoms for at least twelve months after initial infection or until the semen of a male survivor tests negative for Ebola virus on two separate occasions.Survivors develop antibodies against Ebola that last at least 10 years, but it is unclear whether they are immune to additional infections. Cause
EVD in humans is caused by four of six viruses of the genus Ebolavirus. The four are Bundibugyo virus (BDBV), Sudan virus (SUDV), Taï Forest virus (TAFV) and one simply called Ebola virus (EBOV, formerly Zaire Ebola virus). EBOV, species Zaire ebolavirus, is the most dangerous of the known EVD-causing viruses, and is responsible for the largest number of outbreaks. The fifth and sixth viruses, Reston virus (RESTV) and Bombali virus (BOMV), are not thought to cause disease in humans, but have caused disease in other primates. All five viruses are closely related to marburgviruses. Virology
Ebolaviruses contain single-stranded, non-infectious RNA genomes. Ebolavirus genomes contain seven genes including 3-UTR-NP-VP35-VP40-GP-VP30-VP24-L-5-UTR. The genomes of the five different ebolaviruses (BDBV, EBOV, RESTV, SUDV and TAFV) differ in sequence and the number and location of gene overlaps. As with all filoviruses, ebolavirus virions are filamentous particles that may appear in the shape of a shepherds crook, of a "U" or of a "6," and they may be coiled, toroid or branched.
It is believed that this is the reason researchers have observed pig to primate transmission without physical contact, but no evidence has been found of primates being infected without actual contact, even in experiments where infected and uninfected primates shared the same air. Initial case
Although it is not entirely clear how Ebola initially spreads from animals to humans, the spread is believed to involve direct contact with an infected wild animal or fruit bat. Besides bats, other wild animals sometimes infected with EBOV include several species of monkeys such as baboons, great apes (chimpanzees and gorillas), and duikers (a species of antelope).Animals may become infected when they eat fruit partially eaten by bats carrying the virus. Fruit production, animal behavior and other factors may trigger outbreaks among animal populations.Evidence indicates that both domestic dogs and pigs can also be infected with EBOV. Dogs do not appear to develop symptoms when they carry the virus, and pigs appear to be able to transmit the virus to at least some primates. Although some dogs in an area in which a human outbreak occurred had antibodies to EBOV, it is unclear whether they played a role in spreading the disease to people. Reservoir
The natural reservoir for Ebola has yet to be confirmed; however, bats are considered to be the most likely candidate. Three types of fruit bats (Hypsignathus monstrosus, Epomops franqueti and Myonycteris torquata) were found to possibly carry the virus without getting sick. As of 2013, whether other animals are involved in its spread is not known.