Nipah virus
Nipah virus was identified in 1999 when it caused an outbreak of neurological and respiratory disease on pig farms in peninsular Malaysia, resulting in 105 human deaths and the culling of one million pigs (Field et al., 2001). In Singapore, 11 cases including one death occurred in abattoir workers exposed to pigs imported from the affected Malaysian farms.
Symptoms of infection from the Malaysian outbreak were primarily encephalitic in humans and respiratory in pigs. Later outbreaks have caused respiratory illness in humans, increasing the likelihood of human-to-human transmission and indicating the existence of more dangerous strains of the virus.
Four more outbreaks of Nipah virus have occurred since 1999, all of them in Bangladesh. As with Hendra virus, the timing of the outbreaks indicates a seasonal effect.
2001 April – May, Meherpur district: 13 cases with nine fatalities (69% mortality) (Hsu et al, 2004).
2003 January 2003, Naogaon district: 12 cases with eight fatalities (67% mortality) (Hsu et al, 2004).
2004 January – February, Manikganj and Rajbari provinces: 42 cases with 14 fatalities (33% mortality).
2004 19 February – 16 April, Faridpur district: 36 cases with 27 fatalities (75% mortality). Epidemiological evidence strongly suggests that this outbreak involved person-to-person transmission of Nipah virus, which had not previously been confirmed in humans. 92% of cases involved close contact with at least one other person infected with Nipah virus. Two cases involved a single short exposure to an ill patient, including a rickshaw driver who transported a patient to hospital. In addition, at least six cases involved acute respiratory distress syndrome which has not been reported previously for Nipah virus illness in humans. This symptom is likely to have assisted human-to-human transmission through large droplet dispersal.
2005 January, Tangail district: 32 cases with 12 fatalities (38% mortality). The virus may have been contracted from drinking palm fruit juice contaminated by fruit bat droppings or saliva.
In addition to these confirmed cases, a suspected outbreak of encephalitis in Siliguri, India occurred in February-March 2001. The official diagnosis of measles was not supported by the clinical or epidemiological evidence, and later testing of samples by the Centers for Disease Control and Prevention in the USA confirmed the presence of Nipah virus (Kumar, 2003).
