Nipah virus (NiV), emerged in Peninsular Malaysia, caused an outbreak of severe febrile encephalitis in humans and respiratory diseases in pigs between 1998 and 1999. By May of 1999, the death of 105 humans and the culling of about 1.1 million pigs were reported. Fruitbats of Pteropid species were identified as the natural reservoir hosts. The epidemiological studies suggested that NiV was introduced into pig farms by fruitbats, and was than transmitted to humans (mainly pig farmers) and other animals such as dogs, cats and horses. In 2004, NiV reappeared in Bangladesh with greater lethality. In contrast to the Malaysia case, epidemiologic characteristics of this outbreak suggested the possibility of fruitbats-to-person, or person-to-person transmission. In this article, the epidemiological comparison between two outbreaks in Malaysia and Bangladesh, and the new-trends of virological studies of NiV will be discussed.
A novel indirect fluorescent antibody test (IFAT) for detection of IgM against Nipah virus (NiV) was developed using HeLa 229 cells expressing recombinant NiV nucleocapsid protein (NiV-N). The NiV IFAT was evaluated using three panels of sera: a) experimentally produced sera from NiV-N-immunized/pre-immunized macaques, b) post-infection human sera associated with a Nipah disease outbreak in the Philippines in 2014, and c) human sera from a non-exposed Malaysian population. Immunized macaque sera showed a characteristic granular staining pattern of the NiV-N expressed antigen in HeLa 229 cells, which was readily distinguished from negative-binding results of the pre-immunized macaque sera. The IgM antibody titers in sequential serum samples (n = 7) obtained from three Nipah patients correlated well with previously published results using conventional IgM capture ELISA and SNT serology. The 90 human serum samples from unexposed persons were unreactive by IFAT. The IFAT utilizing NiV-N-expressing HeLa 229 cells to detect IgM antibody in an early stage of NiV infection is an effective approach, which could be utilized readily in local laboratories to complement other capabilities in NiV-affected countries.