NAME: Nipah virus.
CHARACTERISTICS: Belongs to the genus Henipavirus, within the family Paramyxoviridae (3, 7). Nipah virus is named after the Malaysian location where it was first detected (Kampung Baru Sungai Nipah), is pleomorphic (varying in size from 120 to 500 nm), non-segmented, and has a single-stranded, negative sense RNA geWnome ( 2, 4 , 11, 12). At the electron microscope level, Nipah virus has a herring-bone-like appearance (11).
PATHOGENICITY/TOXICITY: Nipah virus can cause a neurologic and respiratory disease, with symptoms including fever, headache, drowsiness, nausea, confusion, vomiting, cough, giddiness, and myalgia ( 4, 8, 12, 13). The infection may be mild or sub-clinical in 8 to 15% of cases, or the disease may progress to encephalitis and coma (3, 4, 8, 12, 13). Neurological signs include a reduced level of consciousness, abnormal doll's eye reflex, pinpoint pupils, and seizures (13). Fifty percent of clinically apparent cases are fatal, with death probably resulting from severe brainstem involvement (1, 3). In survivors, there is a potential for relapse months to years after infection -occurs in approx 8% (14). Some people can also develop atypical pneumonia and severe respiratory problems, including acute respiratory distress.
EPIDEMIOLOGY: The first outbreak occurred in Malaysia between 1998 and 1999 among pig farmers and residents of villages where pigs were farmed, and consisted of 265 cases including 105 fatalities (4, 9, 11, 12). A second outbreak occurred in Singapore in 1999 among abattoir workers who had handled pigs imported from the original outbreak in Malaysia, and resulted 11 cases including 1 death (4, 9, 10, 12). Further outbreaks of a Nipah virus-associated encephalitis occurred in Bangladesh and India in 2001, 2003, 2004, and 2007 (15-19). The case mortality rate in the 2004 outbreak in Bangladesh was approximately 70%, which is significantly higher than any other outbreak to date (16).
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: The mechanism for the transmission of the virus from fruit-bats to animals is unknown, but may involve consumption of fruit contaminated with urine or saliva from infected bats (6). Transmission from animals to humans appears to occur by direct contact with contaminated tissues/body fluids of infected animals, especially pigs (3, 4, 8, 10, 11, 13, 20, 22). Other infected animals, such as cats and dogs, may also be involved in spreading the virus (11). Human to human transmission is likely to occur by direct exposure to an infectious inoculum shed in the respiratory secretions of the infected individual, as well as by close physical interaction and frequent contact with the infected individual’s saliva (18, 23).
COMMUNICABILITY: Human-to-human transmission has been documented in several of the more recent outbreaks in Bangladesh, before which human-to-human transmission was considered to be a rare event (1, 17-19, 24). The cases in Bangladesh were seen in the absence of any obvious zoonotic source and Nipah virus was likely transmitted by large droplet transmission from sneezing or coughing (17, 18). In the 2007 Bangladesh outbreak, however, 50% of Pteropus bats sampled in the region 1 month after the outbreak had antibodies to Nipah virus, suggesting bats as a possible zoonotic source (19). Nosocomial infections are possible (via respiratory droplets and urine), although their incidence is thought to be rare (1, 24).
ZOONOSIS: Yes. Usually requires the transmission of virus from fruit-bats to other animal species, with subsequent transmission from these species (especially pigs) to humans (3, 4, 6, 20, 24). Viral transmission can also occur via the human consumption of raw date palm juice fruit contaminated with virus containing fruit-bat urine or saliva (16).
VECTORS: None known.
PHYSICAL INACTIVATION: Samples containing Nipah virus diluted in phosphate buffered saline containing Tween-20 and Triton-X100 have been heat inactivated at 56ºC for 30 minutes (5).
SURVIVAL OUTSIDE HOST: Unknown.
SURVEILLANCE: Monitor for symptoms. Diagnosis can be done by serology, ELISA, serum neutralization, virus isolation, electron microscopy, immunohistochemistry, or diagnostic PCR assay (1-3, 5, 8, 10, 12).
Note: All diagnostic methods are not necessarily available in all countries.
PROPHYLAXIS: None (28).
LABORATORY-ACQUIRED INFECTIONS: Health care workers and pathologists have been documented to have been accidentally exposed to Nipah virus, but after stringent testing, none were shown to have contracted the virus (17, 21).
SOURCES/SPECIMENS: Body fluids such as respiratory droplets, throat secretions, nasal secretions, saliva, blood, urine, cerebrospinal fluid, and tissues of infected individuals, and animals (3, 8, 10, 21, 24).
SPECIAL HAZARDS: Unknown.
RISK GROUP CLASSIFICATION: Risk Group 4 (29).
CONTAINMENT REQUIREMENTS: Containment Level 4 facilities, equipment, and operational practices for work involving infected or potentially infected materials, animals, or cultures.
PROTECTIVE CLOTHING: Personnel entering the laboratory must remove street clothing, including undergarments, and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashes (30).
OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) in combination with a positive pressure suit, or within a class III BSC. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are loaded or unloaded in a biological safety cabinet. The integrity of positive pressure suits must be routinely checked for leaks. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activities (30).
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up.
DISPOSAL: Decontaminate all materials for disposal from the containment laboratory by steam sterilisation, chemical disinfection, incineration, or by gaseous methods. Contaminated materials include both liquid and solid wastes.
STORAGE: In sealed, leak-proof containers that are appropriately labelled and locked in a Containment Level 4 lab.
REGULATORY INFORMATION:The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: January, 2012
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2012