MATERIAL SAFETY DATA SHEET - INFECTIOUS SUBSTANCES

SECTION I - INFECTIOUS AGENT

NAME: West Nile Virus

SYNONYM OR CROSS REFERENCE: West Nile encephalitis virus, West Nile encephalitis, WN virus, WNV, arbovirus, viral encephalitis

CHARACTERISTICS: single stranded, positive sense RNA; lipid-enveloped virion 50 nm diameter; family Flaviviridae, genus Flavivirus ⁽¹⁾, Japanese encephalitis antigenic complex which includes the Japanese encephalitis, Murray Valley encephalitis, St. Louis encephalitis, and Kunjin viruses ⁽²⁾

SECTION II - HEALTH HAZARD

PATHOGENICITY: The disease is characterized by the sudden onset of a febrile "flu-like" illness. Most infections are mild to moderate and symptoms can include malaise, anorexia, nausea, vomiting, eye pain, headache, myalgia, rash and lymphadenopathy ⁽³⁾. More severe infections result in aseptic meningitis or encephalitis and symptoms can include meningismus, mental status changes, occasional seizures, and coma. The overall case fatality rate for WNV ranges from 4% to 11% ⁽³⁾. Risk of severe neurologic disease after infection increases markedly among persons 50 years of age and older ⁽³⁾.

EPIDEMIOLOGY: It is indigenous to Africa, Asia (India and Indonesia), Australia and Europe. In recent years, local epidemics have been reported in North America, Romania, Russia, southern France, Israel and the Cape Province of South Africa ⁽⁴⁾. In temperate and subtropical zones, cases occur in summer or early fall when mosquitoes are most abundant ⁽⁴⁾.

HOST RANGE: Mammal, reptile ^(5,6) and avian hosts ⁽⁴⁾. Mammals (including humans, horses and squirrels) are considered incidental or dead-end hosts ^(1,4), however viraemia in avians can be sufficient for transmission of infection ⁽¹⁾.

INFECTIOUS DOSE: Unknown.

MODE OF TRANSMISSION: Spread by the bite of an infected mosquito. Evidence has also been found demonstrating indirect transmission from person-to-person through blood transfusions ⁽⁷⁾ and organ donations ⁽⁸⁾. West Nile virus can also be transmitted from an infected animal-to-person through punctures and cuts.

INCUBATION PERIOD: Usually 3-14 days, with symptoms lasting 3-6 days ⁽³⁾.

COMMUNICABILITY: Not transmitted directly from person-to-person.

SECTION III - DISSEMINATION

RESERVOIR: Birds are the amplifying hosts ^(3,4,9).

ZOONOSIS: Yes, from infected birds via mosquito bites; it maintains an enzootic cycle involving mosquitoes and birds ^(3,4,9).

VECTORS: Mosquitoes (primarily involving Culex sp. mosquitoes) ^(3,4,9).

SECTION IV - VIABILITY

DRUG SUSCEPTIBILITY: N/A

SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to disinfectants - 3-8% formaldehyde, 2% glutaraldehyde, 2-3% hydrogen peroxide, 500 to 5000ppm available chlorine, alcohol, 1% iodine and phenol iodophors and other organic solvents/detergents ⁽¹⁰⁾.

PHYSICAL INACTIVATION: Inactivated by ultraviolet light and gamma irradiation; rapidly inactivated at high temperatures: at 50° C, 50% of infectivity is lost in 10min; and, totally inactivated within 30 min. at 56° C ⁽¹⁰⁾.

SURVIVAL OUTSIDE HOST: 10 fold decrease in titer per 24hour period at 28° C ⁽¹¹⁾.

SECTION V - MEDICAL

SURVEILLANCE: Most West Nile viral infections are asymptomatic ⁽⁴⁾. The associated clinical symptoms are non-specific and a diagnosis cannot reliably be made on clinical grounds alone. Serological studies or isolation of virus from blood can be applied for identification of the virus ⁽⁴⁾.

FIRST AID/TREATMENT: No specific treatment. In more severe cases, intensive supportive therapy is indicated ^(3,4), often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care. As there is no specific treatment, prevention by means of mosquito control, use of repellants and specific biosafety measures when handling specimens/animals is important ⁽¹²⁾.

IMMUNIZATION: None available to date.

PROPHYLAXIS: None available.

SECTION VI - LABORATORY HAZARDS

LABORATORY-ACQUIRED INFECTIONS: Over 20 cases reported up to 2002 ^(13,14).

SOURCES/SPECIMENS: Serum, cerebrospinal fluid, other tissues (e.g. brain), infected arthropods

PRIMARY HAZARDS: Aerosol producing procedures, percutaneous inoculations.

SPECIAL HAZARDS: Naturally or experimentally infected animal, including arthropods (mosquitoes)

SECTION VII - RECOMMENDED PRECAUTIONS

CONTAINMENT REQUIREMENTS: Containment Level 2 facilities ⁽¹⁵⁾ using Containment Level 3 operational practices ⁽¹⁵⁾, are recommended for all handling of human and animal clinical specimens ⁽¹⁶⁾. Containment Level 3 facilities, containment equipment and practices, are recommended for virus isolation and laboratory manipulation of the West Nile virus ⁽¹⁶⁾.

PROTECTIVE CLOTHING: Laboratory coat, gloves and gown (tie in back and tight wrists) must be worn when working with infected materials.

OTHER PRECAUTIONS: None

SECTION VIII - HANDLING INFORMATION

SPILLS: Allow aerosols to settle: wearing protective clothing, the spill must be covered promptly with a paper towel and disinfectant poured gently on towel, starting at perimeter and working towards the centre; allow sufficient contact time (30 min) before clean up.

DISPOSAL: Decontaminate before disposal: steam sterilization, incineration.

STORAGE: In sealed containers that are appropriately labelled and locked in a containment Level 3 facility.

SECTION IX - MISCELLANEOUS INFORMATION

Date prepared: July, 2003

Prepared by: Office of Laboratory Security, PHAC

Although the information, opinions and recommendations contained in this Material 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.

REFERENCES

1. Prowse, CV. An ABC for West Nile virus. Transfusion Medicine 2003;13:1-7.
2. Heinz FX, Collet MS, Purcell RH, Gould EA, Howard CR, Houghton M, et al. Family: Flaviridae. In: Van Regenmortel MHV, Fourquet CM, Bishop DHL, Carstens EB, Estes MK, Lemon SM, et al., editors. Virus Taxonomy: Classification and Nomenclature of Viruses. 7th Report of the International Committee on Taxonomy of Viruses. San Diego: Academic Press; 1999. p. 859-878
3. Peterson LR, Marfin AA. West Nile Virus: A Primer for the Clinician. Annals of Internal Medicine. 2002;137:173-179.
4. Campbell GL, Marfin AA, Lanciotti RS and Gubler DJ. West Nile virus [Review]. Lancet Infectious Diseases 2002;2:519-529.
5. Miller DM, Mauel MJ, Baldwin D, Burtle G, Ingram D, Hines II ME, et al. West Nile virus in farmed alligators. Emerg Infect Dis [serial online] 2003 Jul[cited 2003 June 19];9(7). Available from: http://www.cdc.gov/ncidod/eid/vol9no7/03-0085.htm
6. Steinman A, Banet-Noach C, Tal S, Levi O, Simanov L, Perk S, et al. West Nile virus infection in crocodiles. Emerg Infect Dis [Serial Online] 2003 Jul [cited 2003 June 19];9(7). Available from: http://www.cdc.gov/ncidod/eid/vol9no7/02-0816.htm
7. Centers for Disease Control and Prevention. Investigations of West Nile Virus Infections in Recipents of Blood Transfusions. MMWR Morb Mortal Wkly Rep. 2002;51(43):973-974.
8. Iwamoto M, Jernigan DB, Guash A et al. Transmission of West Nile Virus from an Organ Donor to Four Transplant Recipiants. The New England Journal of Medicine. 2003;348:2196-2203.
9. Centers for Disease Control and Prevention. Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for Surveillance, Prevention and Control. April 2001.
10. Fields, B. "Flaviviruses." In Fields Virology, Third Edition. Edited by Fields et al. New York: Lippincott-Raven, 1996.
11. Mayo DR, Beckwith WH. Inactivation of West Nile Virus during Serological Testing and Transport. Journal of Clinical Microbiology 2002; 40:3044-3046
12. Health Canada. Occupational Health Advisory West Nile Virus. June 2003. http://www.phac-aspc.gc.ca/wnv-vwn/bio_e.html
13. Collins CH, Kennedy DA. Laboratory-acquired Infections: History, incidence, causes and preventions. Fourth Edition. Oxford. Butterworth-Heinemann. 1999.
14. Centers for Disease Control and Prevention. Laboratory-Acquired West Nile Virus Infections - United States, 2002. Morb Mortal Wkly Rep. 2002;51:1133-1135
15. Health Canada. Laboratory Biosafety Guidelines. 1996. http://www.phac-aspc.gc.ca/publicat/lbg-ldmbl-96/index.html
16. Health Canada. Biosafety Advisory West Nile Virus. June 2003. http://www.phac-aspc.gc.ca/ols-bsl/wnvbio_e.html

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Health Canada, 2003

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