Nipah virus (NiV) is a zoonotic paramyxovirus that was first recognized in 1999 as the causative agent of outbreaks of human encephalitis in Malaysia and Singapore, in association with severe respiratory and neurological disease in pigs. Since then, outbreaks of NiV encephalitis have also occurred in Bangladesh during 2001-2004, but without an association to infected swine or other animals. Although NiV infections typically result in acute encephalitis with high mortality, other clinical manifestations, including asymptomatic infection, relapsed encephalitis, and pulmonary disease, have been observed. The article will summarize the virology, epidemiology, clinical features, treatment, and control and prevention of NiV infections in humans.