Wilderness Underfoot: The voyage of the West Nile virus

StoryImage( ‘/Images/Story//Auto-img-11865235596986.jpg’, ”, ‘A variety of mosquito species can carry West Nile virus – including Culex pipiens (above). The virus is transmitted from infected animals by mosquitoes, which also bite humans. At a width of barely 50 nanometers across, the virus is (right) very tiny. (A nanometer is only 1 billionth of a meter.) The West Nile virus is part of the flavivirus family, which also includes dengue virus and yellow fever virus. Despite its size, West Nile virus has been deadly. In addition to its danger to humans, the virus has devastated populations of many bird species — particularly crows, chickadees and robins. Birds are the main host, and once infected, the virus rapidly multiplies in their bodies. The next mosquito that comes along will inadvertently pick up the virus and transmit it to the next host. West Nile virus can also infect domestic pets and mammals such as bats, squirrels, and skunks.‘);
StoryImage( ‘/Images/Story//Auto-img-11865235729653.jpg’, ”, ”);
StoryImage( ‘/Images/Story//Auto-img-118652358314726.jpg’, ”, ”);

This 1,000-year-old virus has arrived and established itself in North America.

Although it was discovered in Uganda only 70 years ago, the West Nile virus is estimated to have been around for at least a millennium. Found in Africa, the Middle East, and parts of Eurasia, the virus has spread north and west, primarily through migratory birds that carry the infection.

The first known appearance of West Nile disease in the Western Hemisphere was in August 1999, when unusual death counts of birds were tied in to human cases. Over the next few years, the virus would spread across the U.S. and into Canada.

The Centers for Disease Control (CDC) reports that last year, more than 4,000 people in the U.S. were known to be infected, and 177 died. The worst year so far was 2002, when more than 9,800 people were infected, and 264 died.

According to the CDC, “[West Nile disease] symptoms include fever, headache, tiredness, and body aches, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands.” But the most deadly aspect of the disease is its potential for causing encephalitis (inflammation of the brain) and meningitis (inflammation of the membranes that protect the central nervous system). Interestingly, a small number of people may be infected and notice no symptoms at all.

The CDC recommends avoiding exposure to mosquitos, using repellent when outdoors, wearing long sleeves and pants when weather permits, and removing water sources where mosquitos breed. Also, repair any openings in your home, such as tears in screens, where mosquitoes may enter.

from the August 8-14, 2007, issue

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