Skip navigation Bye Bye Birdie
POSTED APR 10, 2003


1. Spreading like wild virus

2. The study of birds

3. Making sense of West Nile






West Nile virus is breaking all the rules, and nobody can feel confident making predictions.





In less than four years, West Nile virus spread across the heart of North America. Image: USGS National Wildlife Health Center









Widespread spraying against mosquitoes was a reflexive response after West Nile entered the Western Hemisphere in summer, 1999. A truck sprays insecticide to kill mosquitoes in Manhattan, New York, on Monday, Sept. 13, 1999. Critics say such sprays are ineffective against mosquitoes, but dangerous to people and the environment. AP Photo/Ed Betz


Vilifying a virile virus
Known for exporting TVs, toys and clothing, China is making headlines with an ominous export. By April 5, severe acute respiratory syndrome (SARS) had sickened 2,416 people in 20 countries and killed 89.

Iridescent black crow with a thick black beak stands in the grass. The American crow is the primary victim of West Nile virus Photo: USGS.

Observers credit government secrecy for accelerating SARS's spread beyond Guangzhou Province, where it first appeared last fall. At any rate, tourism and business -- aside from protective face mask sales -- have tanked in China and especially Hong Kong.

No media silence attended the arrival of West Nile virus in New York City in 1999. You can catch the tenor of the discussion from an Aug. 13, 2000, New York Post headline: "2 Catch Skeeter Virus -- New Cases Spur Pesticide Assault." Like SARS, West Nile is a fast-spreading viral disease. In less than four years, West Nile has reached 44 states, six Canadian provinces, the Dominican Republic and northern Mexico.

Although West Nile has sickened 4,161 Americans and killed 277, it is primarily a bird disease. To date, the virus has been found in 158 species of birds and 18 other vertebrates, including alligators and horses -- see "Researchers Scramble ..." in the bibliography).

While most infected animals -- human and otherwise -- never appear sick, West Nile can cause a deadly inflammation of the brain - encephalitis.

Map of North American shows the majority of U.S. states colored pink to indicate the presence of West Nile, with only Oregon, Nevada, Utah, and Arizona remaining negative.

Where is the virus headed?
Insecticide pours from a  device in the bed of a pickup truck as the truck moves down a nighttime city street. Normal people worry about the human epidemic. Here at the Why Files, we're thinking about birds. Where will the avian epidemic end? Will some birds go extinct?

West Nile is new to the Americas, so both humans and birds lack immunity to it. Epidemics can ravage newly exposed populations. When European conquerors brought smallpox across the Atlantic 500 years ago, the virus decimated native Americans. When avian pox and avian malaria reached the susceptible, isolated of Hawaii, many birds went extinct.

West Nile virus

Those parallels are unsettling, but not necessarily a good guide to West Nile, which is far less deadly than smallpox. Indeed, the experts we consulted were baffled, boggled and bewildered by West Nile. Reflecting the views of many, Carolee Caffrey, an ornithologist and science associate at the National Audubon Society, said, "People said they'd like to look to other flaviviruses [the viral family that includes West Nile] for information and guidance, but West Nile virus is so different. The host range is way broader than other flaviviruses, the number of mosquitoes that can be carriers is way broader. When other flaviviruses were introduced to the continent, the rapidity of their spread was much slower. West Nile virus is breaking all the rules, and nobody can feel confident making predictions."

Here's our prediction. You are going to turn the page...

The Why Files

There are 1 2 3 pages in this feature.
Bibliography | Credits | Feedback | Search

Terry Devitt, editor; Sarah Goforth, project assistant; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive

©2003, University of Wisconsin, Board of Regents.