Nipah virus infection: An emerging zoonosis: A review

Abstract

Nipah virus (NiV) is a zoonotic, highly pathogenic, biosafety level 4 (BSL4) virus within the family Paramyxoviridae, genus Henipavirus. Humans infected with NiV suffer primarily from severe encephalitis with pulmonary involvement in high percentage of patients, and with fatal outcome in about 40% or more of laboratory confirmed cases, depending on the outbreak. Encroachment of human populations into wildlife habitat is the prime cause for the emergence of these diseases. Emergence also depends on the presence of domestic animal ‘amplifier’ hosts, changes in agricultural operations and human behaviour. In case of NiV, it appears that change in the distribution of flora associated with intensively managed farms (i.e. introduction of fruit bats) along with a probability of viral transmission between co-evolved (fruit bats) and naive (pig) hosts. Serologic studies also suggested that NiV infection occurred in dogs, cats and two polo ponies and in bats in the outbreak area in Malaysia. Two key features of this outbreak were the fatal encephalitis and infection of human having direct contact with pigs. Pathologic studies of infected human and pig tissues provided plausible explanations for these two features of the outbreak. Studies on the status of NiV is of national importance as the disease has occurred and re-emerged in Bangladesh; moreover, there is a very large population of pigs in the north eastern states. The combination of the pathogen prevalence in the near vicinity, along with presence of susceptible reservoir hosts in large numbers could be extremely favourable for emergence of this disease. Better understanding of the NiV infection in swine would be critical for developing control measures, before another NiV disease outbreak initiate in swine.