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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 to Protect Outdoor Workers
from West Nile Virus Exposure

Image of mosquito Outdoor Workers Men loading tires onto a truck Man shoveling dirt

Introduction

Disease:

The West Nile virus (WNV) is spread to humans from the bite of an infected mosquito. The virus normally passes 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.

Occupational Risk

man on tractor plowing field
Occupational exposure to WNV is possible. Workers at risk of WNV exposure include those working outdoors when mosquitoes are actively biting—farmers, foresters, landscapers, groundskeepers and gardeners, painters, roofers, pavers, construction workers, laborers, mechanics, and other outdoor workers. Turkey breeder and alligator farm workers have been infected with WNV. The mode of transmission to these farm workers is uncertain. Laboratory workers who handle WNV-infected tissue and fluids are also at risk of WNV infection if skin penetration or laceration occurs. For more information on WNV exposure among laboratory and field workers, link to the NIOSH fact sheet “Recommendations to Protect Laboratory, Field, and Clinical Workers from West Nile Virus Exposure.”

Occupational groups at risk should receive training that describes and reinforces the potential occupational hazards and risks of WNV exposure and infection. The importance of timely reporting of all injuries and illnesses of suspected occupational origin should be emphasized. A medical surveillance system should be in place which includes the reporting of symptoms consistent with WNV infection and employee absenteeism.

Frequently Asked Questions

Man spraying liquid on debris women in an outdoor vegitable market old man leaning on tractor park service worker with jar full of water

Who Is At Risk Of WNV Exposure?

Anyone who lives or works in an area where there are WNV-infected mosquitoes is at risk of WNV infection. Persons over 50 years of age have the highest risk of severe disease due to WNV infection. Even though older workers may be at higher risk, all workers should be careful to follow the recommendations listed below.

Which Outdoor Workers Are At Risk Of WNV Exposure?

Workers at risk of WNV exposure include those working outdoors when mosquitoes are actively biting—farmers, foresters, landscapers, groundskeepers and gardeners, painters, roofers, pavers, construction workers, laborers, mechanics, and other outdoor workers. Many mosquitoes are most active from dusk to dawn. However, some mosquitoes are active during the day. When possible, avoid working outdoors during mosquitoes’ peak activity times.


jar of standing water with mosqutos inside     

Where Are Mosquitoes Most Commonly Found?

Mosquitoes develop in any standing body of water that persists for more than four days. Stagnant pools, ponds, watering troughs, irrigation ditches, rain barrels, manure lagoons, and other stagnant bodies of water increase mosquito populations. Weedy, bushy, and wooded work environments may also have large mosquito populations. Workers in these environments should protect themselves from mosquito bites.

When Are Mosquitoes Most Active?

Many mosquitoes are most active from dusk to dawn. However, some mosquitoes are also active during the day. When possible, avoid working outdoors during mosquitoes’ peak activity times. When this is unavoidable, use personal protection such as protective clothing and insect repellent to reduce the potential for exposure. 		construction workers at dawn

How Can I Be Protected From WNV Exposure?

Recommendations for Employers

Employers should protect their workers by implementing the following controls:

  • Avoid having workers outdoors when mosquitoes are most active and biting, most often from dusk to dawn.
  • Make insect repellents available to workers.
    • DEET, picaridin, and oil of lemon eucalyptus are effective repellents.
  • Recommend that outdoor workers wear long-sleeved shirts, long pants, and socks when possible.
    • If employee uniforms are provided include long-sleeved shirts and long pants among uniform options.
  • Eliminate as many sources of standing water as possible to decrease mosquito populations. Water that persists for more than four days provides a site for mosquitoes to develop.

    • Change the water twice a week in animal drinking troughs, birdbaths, and other water containers.
    • Add an aerator to ponds and water gardens to keep the water circulating or add fish that will eat the mosquito larvae or adults.
    • Remove discarded tires from the worksite.
    • Turn over, cover, or remove equipment such as tarps, buckets, barrels, wheel barrows, and containers to avoid water accumulation.
    • Place drain holes in containers that collect water and cannot be discarded.
    • Clean out rain gutters.
    • Remove debris—leaves, twigs, trash—from ditches frequently.
    • Fill in or drain ruts and other areas that accumulate water.

Recommendations for Workers

Outdoor workers can reduce their risk of WNV exposure by taking the following action steps:

  • Insect Repellent

    • Apply insect repellent to exposed skin.
    • Carefully follow label directions for repellent use.
    • Do not apply pump or aerosol products directly to the face. These products should be sprayed onto the hands and then carefully rubbed over the face, avoiding the eyes and mouth.
    • Use repellents at the lowest effective concentrations.
    • Wash skin treated with insect repellent with soap and water after returning indoors.
  • Clothing

    • Wear long-sleeved shirts, long pants, and socks when working outdoors.
    • Spray clothing with products containing DEET or permethrin, as mosquitoes may penetrate thin clothing.

      • Permethrin should only be used on clothing; do not apply it directly to skin.
    • Wash clothing treated with insect repellent before wearing it again.
    • Do not apply repellent to skin that is under clothing.

dead crow

What Should I Do If I Have To Handle 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 I Do If I Develop Symptoms Of WNV?

Any worker who develops mild symptoms of WNV such as fever, fatigue, headache, and muscle or joint pain or severe symptoms such as high fever, stiff neck, disorientation, tremors, muscle weakness, and paralysis should contact their health care provider immediately. The period from the infected bite to developing symptoms is reported to be 3 to 14 days.		 doctor

Is There Treatment Available If I Am Infected With WNV?

No specific treatment exists for WNV infection. Treatment consists of supportive care to treat the symptoms. Currently, no approved vaccine exists to prevent WNV infection in humans.

Additional Resources

For updated information on WNV:

CDC West Nile Virus Home Page:
http://www.cdc.gov/ncidod/dvbid/westnile/

For more information about insect repellents:

CDC: Updated Information Regarding Insect Repellents
http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm

CDC: Insect Repellent Use and Safety
http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm

U.S. EPA: How to Use Insect Repellents Safely
http://www.epa.gov/pesticides/factsheets/insectrp.htm

The National Pesticide Information Center (NPIC) can be contacted by telephone at
1–800–858–PEST (1–800–858–7378), 9:30 a.m. to 7:30 p.m. eastern standard time, 7 days/week, or link to the NPIC Web site:
http://npic.orst.edu

 

Reviewed June 29, 2005

Safer - Healthier - People
For additional information, contact NIOSH:
1-800-35-NIOSH
(1-800-356-4674)
Fax: 513-533-8573
or visit the NIOSH Web site:
www.cdc.gov/niosh
NIOSH Fact Sheet


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