The Nipah has infected a wide range of animals and caused severe disease and death in people, according to the WHO.
During the first recognised outbreak, which took place in Malaysia and Singapore, most human infections resulted from direct contact with sick pigs or their contaminated tissue.
Transmission is thought to have happened via unprotected exposure to secretions from the pigs, or unprotected contact with the tissue of the sick animal.
Subsequent outbreaks took place in Bangladesh and India, but this time, through consumption of fruits or fruit products contaminated with urine or saliva from infected fruit bats.