Flu-like illness complicated by pneumonia or encephalitis; [CCDM]
The first human cases were recognized in 1994 and 1999. The Hendra cases followed close contact with sick horses in Australia, and the Nipah cases occurred in pig farmers in Malaysia. Patients developed encephalitis and pneumonitis. The case-fatality rate was 40-75%. Fruit bats of the Pteropus genus appear to be the major hosts, and antibody studies suggest that related viruses exist in an area stretching from Oceania to the Middle East, and including Africa. There was evidence of person-to-person spread in the outbreaks in India and Bangladesh. [CCDM, p. 428-31] Hendra and Nipah viruses appear to be old viruses that emerged because of habitat changes of flying foxes (fruit bats). [PPID, p. 1975]
Since 1994, there have been only 7 cases of Hendra virus infecting humans after exposure to sick horses. Four of the seven patients died from severe respiratory disease. Findings included fever, cough, sore throat, myalgia, cervical lymphadenopathy, thrombocytopenia, and abnormal liver function tests. [PPID, p. 1978-9]
Eleven abattoir workers developed encephalitis or pneumonia and one died after Nipah virus infections in Singapore in 1999. All infected workers had direct contact with live pigs. [J Infect Dis 2000;181(5):1760-3] Since 1998, there have been 276 cases of Nipah virus infections in Malaysia and Singapore (38% case fatality) and 224 cases in India and Bangladesh (66% case fatality). In the outbreaks in India and Bangladesh, there was evidence of transmission from person to person and by ingestion of contaminated date palm sap. Initial symptoms included fever, headache, dizziness, and vomiting with about 50% of patients developing CNS disease with signs of encephalitis and brain stem dysfunction (areflexia, hypotonia, myoclonus, and ataxia). Complications included sepsis, GI bleeding, and renal failure. Respiratory disease was more common in the India and Bangladesh outbreaks and 5 of these patients developed ARDS. Some patients with encephalitis/meningitis had CSF pleocytosis with a predominance of neutrophils. Some patients with encephalitis had persistent impairments including encephalopathy, focal weakness, and cranial palsies. Other lab abnormalities were leukopenia (11%), thrombocytopenia (30%), and elevated liver function tests (33%). MRI is sensitive for detecting encephalitis in Nipah infected patients. [PPID, p. 1975-8]
For updated text and symptoms of infectious diseases, see iddx.com.
Nipah virus: usually <2 weeks (range of several days to 2 months); Hendra virus: 5-21 days; [PPID, p. 1977, 1979]