Nipah, a bat-borne virus, was first identified during a 1998-99 outbreak in Malaysia. It causes severe disease, most commonly encephalitis and pneumonia. Among symptomatic cases, the fatality rate ranges from 40 to 75 per cent, and survivors may be left with profound neurological damage. There are currently no vaccines, treatments or rapid tests, making it difficult to diagnose and untreatable once infection occurs. Nipah does not spread easily between humans — but it can. Person-to-person transmission, including superspreading events, has occurred in Bangladesh and India, often in hospitals.