2007 West Nile Virus Risk

Third in our Risk Management Series is West Nile virus.

West Nile virus is not a river in Egypt…

West Nile virus (WNV) is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. WNV is mainly transmitted by the well known blood-feeding arthropod, the mosquito.

The risk of West Nile virus in Virginia is low.

WNV first appeared in North America in 1999, with encephalitis reported in humans and horses. WNV has emerged in recent years in temperate regions of Europe and North America, presenting a threat to public and animal health. The most serious manifestation of WNV infection is fatal encephalitis (inflammation of the brain) in humans and horses, as well as mortality in certain domestic and wild birds. Not until early 2002 has WNV been a significant cause of human illness in the United States—only 5 Virginia cases reported in 2006. West Nile virus was first identified in the West Nile District of Uganda in 1937 and only became recognized as a cause of severe human meningitis or encephalitis (inflammation of the spinal cord and brain) in elderly patients during an outbreak in Israel in 1957.

• Arthropod-borne viruses (termed "arboviruses") are viruses that are maintained in nature through biological transmission between susceptible vertebrate hosts by blood-feeding arthropods (mosquitoes, sand flies, ceratopogonids "no-see-ums", and ticks). Vertebrates can become infected when an infected arthropod bites them to take a blood meal.

WNV Symptoms?

People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito.

• Serious Symptoms in a Few People. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

• Milder Symptoms in Some People. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks.

• No Symptoms in Most People. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all.

The easiest and best way to avoid WNV is to prevent mosquito bites.

• When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package.

• Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.

• Make sure you have intact screens on your tent windows and doors to keep mosquitoes out.

Earth Connection staff will throughout the year attempt to rid the local area of mosquito breeding sites by emptying standing water from flowerpots, buckets and barrels. However, there are many small swampy areas, natural cavities and unruly neighbors that might harbor a very significant population of mosquitoes.