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NIOSH Fact Sheet
The National Institute for Occupational Safety and Health (NIOSH) is the federal agency responsible for conducting research and making recommendations for the prevention of work-related disease and injury. NIOSH is part of the Centers for Disease Control and Prevention (CDC).

Recommendations for Protecting Laboratory, Field, and Clinical Workers From West Nile Virus Exposure

Image of mosquito lab worker crow Image of mosquito 

Introduction

Disease:

The West Nile virus (WNV) is most often spread to humans from the bite of an infected mosquito. The virus normally cycles between mosquitoes and birds. However, people may also be infected if they are bitten by a WNV-infected mosquito.

The most likely route of WNV infection is through the bite of an infected mosquito. In addition, WNV may be spread through organ transplantation, blood transfusion, or possibly breast milk. Transplacental (mother-to-fetus) infection has occurred. Workers are at risk of WNV infection if their skin is penetrated or cut while handling WNV-infected tissues. Turkey breeder and alligator farm workers have been infected with WNV. The mode of transmission to these farm workers is uncertain.

Most human infections cause either mild flu-like symptoms or no symptoms at all. Mild symptoms may include fever, fatigue, headache, and muscle or joint pain. Although rare, some people may become severely ill. Severe symptoms may include high fever, stiff neck, disorientation, tremors, muscle weakness, and paralysis. Severely affected persons may develop encephalitis, meningitis, or meningoencephalitis—inflammation of the brain, membranes of the brain or spinal cord, or both, respectively. Severe cases of WNV may be fatal. Persons over the age of 50 are at higher risk of severe illness.

History:

WNV was first reported in the United States in New York State in the summer of 1999. Since 1999, WNV has caused more than 16,000 cases of human illness including more than 650 deaths.

Location:

WNV is commonly found in Africa, West Asia, and the Middle East. It was first reported in the United States in New York State in 1999. The geographic range of WNV has expanded annually. In 2004 it was reported throughout the continental United States.

crow scalpel blood sample tube Blue Jay 

Occupational Risk

The most likely way persons become infected with WNV is through the bite of an infected mosquito. Therefore, persons working outdoors when mosquitoes are actively biting are at risk of infection (link to NIOSH Fact Sheet: Recommendations to Prevent West Nile Virus Infection in Outdoor Workers). Aside from outdoor workers, workers in many other occupations are at potential risk of exposure to WNV-infected humans, animals, or their blood or other tissues. Workers at risk include laboratory diagnosticians, researchers, and technicians, veterinarians and their staff, wildlife rehabilitators, ornithologists, wildlife biologists, pathologists, zoo and aviary curators, health care workers, emergency response and public safety personnel, public health employees, and workers in related occupations. For example, workers are at risk of WNV infection if their skin is penetrated or cut while performing necropsies or handling WNV-infected tissues or fluids. Turkey breeder and alligator farm workers have been infected with WNV. The mode of transmission to these farm workers is uncertain.

sharps container biosafety symbol medical gloves 

Recommendations for laboratory and field workers

Outdoor workers may be at increased risk of WNV infection and should be educated about this occupational health issue and available recommendations (link to NIOSH Web Site Fact Sheet: Recommendations to Prevent West Nile Virus Infection in Outdoor Workers).

The following recommendations are for both the laboratory and field workplaces in which transmission of WNV may occur by means other than mosquito bite. Until further studies determine the risk of WNV infection from exposure to infected persons, animals, fluids, or tissues, it is prudent public health practice to minimize such potentially infectious contacts. These are basic recommendations to reduce exposure to blood and other tissues from WNV-infected cases. More stringent protective equipment and work practices should be used when warranted. Biosafety guidelines are available for working with WNV and other microbiological agents in the laboratory.

Recommendations for employers

  • Provide training that describes how WNV is transmitted and reinforces the potential risks of WNV exposure and infection.

  • Provide appropriate personal protective equipment that provides barrier protection including gloves, gowns, safety glasses, and/or face shields.

    • Alternatives to powdered latex gloves should be provided.

  • Stress to employees the importance of timely reporting of all injuries and illnesses.

  • Provide a medical surveillance system that monitors, records, and assesses:

    • symptoms consistent with WNV infection

    • laboratory incidents or accidents involving possible WNV exposure

    • employee absenteeism.

Recommendations for workers

  • Use personal protective equipment that provides barrier protection including gloves, gowns, safety glasses, and/or face shields to avoid dermal and mucous membrane contact with blood and other tissues.

    • Workers conducting necropsies should wear gloves that prevent cutting injuries, such as stainless steel mesh gloves, in addition to medical examination gloves.

  • Wash hands and other skin surfaces with soap and water immediately after contact with blood or other tissues, after removing gloves, and before leaving the workplace.

  • Minimize the generation of aerosols.

  • Handle sharp instruments carefully during use.

  • Use medical devices with safety features when available to avoid sharps-related injuries.

  • Avoid recapping needles.

  • Dispose of sharp instruments carefully after use.

  • Report to the supervisor all needlestick and other sharps-related injuries.

  • Report to the supervisor any laboratory incidents or accidents involving possible WNV exposure.

  • Report to the supervisor any symptoms consistent with WNV infection.

For more information on biosafety, link to "Biosafety in the Laboratory", a CDC Office of Health and Safety presentation:
http://www.cdc.gov/od/ohs/pdffiles/Module%202%20-%20Biosafety.pdf

What precautions should be taken if handling dead animals?

Anyone handling dead animals should wear gloves. Appropriate gloves provide a protective barrier that prevents blood and other body fluids from passing through them. Medical examination gloves are recommended. Cotton, leather, and other absorbent glove materials are not protective. If latex gloves are used they should be reduced protein, powder-free gloves to reduce workers’ exposure to allergy-causing proteins.

What should a worker do who suspects he or she has been infected with WNV?

Any laboratory incidents or accidents involving possible WNV exposure should be immediately reported to the supervisor. Any worker who has health concerns should contact his or her health care provider.

Mild symptoms of WNV infection include fever, fatigue, headache, and muscle or joint pain. Severe symptoms include high fever, stiff neck, disorientation, tremors, muscle weakness, and paralysis. The incubation time from mosquito bite to clinical symptoms is reported to be from 3 to 14 days. No specific treatment exists for WNV infection. Treatment consists of supportive care for the individual. Currently, no approved vaccine exists to prevent WNV infection in humans.

References


CDC [2002a]. Possible West Nile Virus Transmission to an Infant Through Breast-Feeding — Michigan, 2002. MMWR 51(39): 877-878.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5139a2.htm


CDC [2002b]. Update: Investigations of West Nile Virus Infections in Recipients of Organ Transplantation and Blood Transfusion — Michigan, 2002. MMWR 51(39): 879.
http://www.cdc.gov/mmwr/PDF/wk/mm5139.pdf


CDC [2002c]. Intrauterine West Nile Virus Infection — New York, 2002. MMWR 51(50): 1135-36. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5150a3.htm


CDC [2002d]. Laboratory-Acquired West Nile Virus Infections — United States, 2002. MMWR 51(50): 1133-1135.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5150a2.htm


CDC [2003]. West Nile Virus Infection Among Turkey Breeder Farm Workers --- Wisconsin, 2002. MMWR 52(42): 1017-1019.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5242a3.htm


CDC/NIH [1999]. Biosafety in Microbiological and Biomedical Laboratories, 4th edition. Washington, DC: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention and National Institutes of Health, DHHS Publication No. 99-xxxx.
http://www.cdc.gov/od/ohs/biosfty/bmbl4/bmbl4toc.htm


NIOSH [1997]. NIOSH Alert: Preventing Allergic Reactions to Natural Rubber Latex in the Workplace. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, NIOSH, DHHS Publication No. 97-135.
http://www.cdc.gov/niosh/latexalt.html


NIOSH [1999]. NIOSH Alert: Preventing Needlestick Injuries. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, NIOSH, DHHS Publication No. 2000-108.
http://www.cdc.gov/niosh/2000-108.html

Reviewed August 22, 2005

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(1-800-356-4674)
Fax: 513-533-8573
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www.cdc.gov/niosh
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