Surveillance and outbreak alert

Information regarding Nipah virus

  • Nipah virus is an emergent paramyxovirus which causes disease both in human and animals. The outbreak of Nipah virus in human was first recognized in Asia in Malaysia in 1999. In the SEA Region, Nipah virus outbreaks have been confirmed in Bangladesh in 2001, 2003 and 2007, and in India in 2001 and 2007.
  • Nipah virus manifests primarily as encephalitis. It is highly pathogenic to humans, with high case fatality rate, ranging from 40 to 75%.
  • In Malaysia outbreak, transmission occurred primarily through contact with infected swine. In Bangladesh, the infection seems to have ocurred directly from fruit bats (believed to be the reservoir) without involvement of intermediate host (swine). The spread can also occur possibly by droplet infection.
  • Clinical presentation can range from asymptomatic infection to fatal encephalitis. Those infected initially have a sudden onset of flu-like symptoms such as fever, headaches, pain in the muscles, vomiting and sore throat, followed by dizziness, drowsiness, altered consciousness (partial or complete loss of consciousness) and focal neurological signs indicating acute encephalitis. Encephalitis and seizures occur in severe cases. This progresses to coma within 24-48 hours.
  • The incubation period varies from four to 18 days, although an incubation period of as long as 45 days has been reported.
  • Some patients, whose respiratory functions were affected, can also present with an atypical pneumonia with fever, cough and headache. Nipah may also manifest with severe respiratory features, including acute respiratory distress; this has been observed more frequently in the outbreaks since the Malaysia outbreak.
  • The pathogenesis is primarily due to endothelial cell damage resulting in systemic vasculitis of small blood vessels, extensive thrombosis, and necrosis as indicated by clinical and autopsy studies.
  • Involvement of the central nervous system, is especially severe in the brain but direct neuronal infection may also play a role. Abundant viral antigens have been seen in neurons. Other organs such as lungs (as described above), heart and kidneys can also be affected.
  • There are currently no effective therapeutics and vaccines available to treat Nipah virus infection. Intensive supportive care is the mainstay of case management.
  • Interestingly, the epidemiology of Nipah has evolved, with our understanding, from a disease which spread from occupation contact (with pigs) to possibly person to person, and also as a food-borne disease.
  • CDC lists it as a critical potential biological weapon because of its availability, ease of production and dissemination, and high virulence in terms of high mortality and health impact.