Nipah virus (NiV) infection may be asymptomatic but more often causes a severe disease. Case fatality rates vary by outbreak, but are estimated to range from 40% to 75%. The rate was approximately 30% to 40% in the Malaysian outbreak, approximately 70% in Bangladesh outbreaks, and approximately 90% in the Kerala, India outbreak.[22]Goh KJ, Tan CT, Chew NK, et al. Clinical features of Nipah virus encephalitis among pig farmers in Malaysia. N Engl J Med. 2000 Apr 27;342(17):1229-35.
http://www.nejm.org/doi/full/10.1056/NEJM200004273421701
http://www.ncbi.nlm.nih.gov/pubmed/10781618?tool=bestpractice.com
[23]Chong HT, Kunjapan SR, Thayaparan T, et al. Nipah encephalitis outbreak in Malaysia, clinical features in patients from Seremban. Neurol J Southeast Asia. 2000;5:61-7.
http://www.neurology-asia.org/articles/20002_061.pdf
http://www.ncbi.nlm.nih.gov/pubmed/11858542?tool=bestpractice.com
[37]Hossain MJ, Gurley ES, Montgomery JM, et al. Clinical presentation of Nipah virus infection in Bangladesh. Clin Infect Dis. 2008 Apr 1;46(7):977-84.
https://academic.oup.com/cid/article/46/7/977/292786/Clinical-Presentation-of-Nipah-Virus-Infection-in
http://www.ncbi.nlm.nih.gov/pubmed/18444812?tool=bestpractice.com
[10]Arunkumar G, Chandni R, Mourya DT, et al. Outbreak investigation of Nipah virus disease in Kerala, India, 2018. J Infect Dis. 2019 May 24;219(12):1867-78.
https://academic.oup.com/jid/article/219/12/1867/5144922
http://www.ncbi.nlm.nih.gov/pubmed/30364984?tool=bestpractice.com
Patients who survive may develop persistent fatigue, somnolence, and/or neurological impairment. They may also develop late-onset and/or relapsed encephalitis.[36]Abdullah A, Tin Tan C. Henipavirus encephalitis. In: Tselis AC, Booss J, eds. Handbook of clinical neurology, volume 123: neurovirology. New York, NY: Elsevier; 2014.
As of May 2018, there have been a total of 7 cases of Hendra virus (HeV) infection in humans since its discovery in 1994, with 4 fatalities (case fatality rate of 57%).[13]Australian Government Department of Health. Hendra virus CDNA national guidelines for public health units. November 2016 [internet publication].
http://www.health.gov.au/internet/main/publishing.nsf/content/cdna-song-hendra.htm
[36]Abdullah A, Tin Tan C. Henipavirus encephalitis. In: Tselis AC, Booss J, eds. Handbook of clinical neurology, volume 123: neurovirology. New York, NY: Elsevier; 2014.
HeV encephalitis may relapse, as is the case with NiV.[48]O'Sullivan JD, Allworth AM, Paterson DL, et al. Fatal encephalitis due to novel paramyxovirus transmitted from horses. Lancet. 1997 Jan 11;349(9045):93-5.
http://www.ncbi.nlm.nih.gov/pubmed/8996421?tool=bestpractice.com