Most cases of West Nile Virus are probably not acquired in the workplace but there are some workers at risk of WNV infection. Outdoor workers are at risk of WNV infection from the bite of an infected mosquito. Workers who perform necropsies of infected birds or handle WNV-infected tissues or fluids are also at risk of WNV infection if skin penetration or laceration occurs.

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

The West Nile virus (WNV) is most often spread to humans from the bite of an infected mosquito. The virus may also be transmitted in other ways—through organ transplants, blood transfusions, and breast milk, and from mother to fetus. But the risk of such transmission is very low. Occupational exposures have been documented.

Most human infections with WNV (about 80%) cause no symptoms, and about 20% cause flu-like symptoms, including fever, fatigue, headache, and muscle or joint pain. Fewer than 1% of humans infected with WNV become severely ill. Severe symptoms include high fever, stiff neck, disorientation, tremors, muscle weakness, and paralysis. Severely affected persons may develop encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes of the brain or spinal cord). Severe cases may be fatal. People of all ages and conditions may be affected. However, those who are above age 50 or who have had an organ transplant are at increased risk of severe illness.

History of WNV in the United States

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 in the United States.

Occupational Risks of WNV

The most likely route of WNV infection to humans is through the bite of an infected mosquito. Workers at risk of exposure to WNV include those working outdoors when mosquitoes are biting. Outdoor workers at risk include farmers, foresters, landscapers, groundskeepers and gardeners, painters, roofers, pavers, construction workers, laborers, mechanics, and other outdoor workers. Entomologists and other field workers are also at risk while conducting surveillance and other research outdoors.

Workers are also at risk of WNV infection if their skin is penetrated or cut while handling WNV-infected tissues. It is recommended that workers use standard infection control and droplet precautions when working with laboratory specimens or with humans or animals suspected or known to be infected with WNV.

Workers 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, laboratory incidents or accidents involving possible WNV exposures, and employee absenteeism.

* For updates on the geographic range of WNV, the number of human cases, and other current information link to the Centers for Disease Control and Prevention (CDC) West Nile Virus Home Page:
http://www.cdc.gov/westnile/

Revised August 22, 2005