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American Crow, photo by Carolee Caffrey.

These pages are current through June 2005

As the 2005 West Nile virus (WNV) season in temperate North America proceeds, many questions remain unanswered regarding details of transmission cycles, relevant vector biology, the range and responses to infection of host species, the mechanisms underlying the spread of the virus and its ability to “overwinter,” and the effects of WNV on bird and other wildlife populations. Because West Nile is an "emerging" virus in the New World - one that has recently become dramatically common - we are still in the initial stages of piecing together parts of the puzzle, and we still have far to go with respect to understanding what WNV will mean for North, Central, and South American wildlife. Scientists from many fields are contributing to the effort to understand and potentially minimize the negative effects of WNV, which is already infamous for its deadliness, the unusually broad range of animals it can infect, and the remarkable speed with which it advanced across a large geographic area.

West Nile virus is a mosquito-borne infection that can cause encephalitis (inflammation of brain tissue) and/or meningitis (swelling of the tissue that encloses the brain and spinal cord). Native to parts of the Old World, WNV was first detected in North America in the summer of 1999, in New York City, NY; a dead crow at the Bronx Zoo was one of the first harbingers of what was to come. Within three months, WNV had spread to Connecticut and New Jersey, leaving tens of thousands of dead birds in its wake¹. Over the subsequent five and a half years, it has continued to spread across the continent, and by the end of 2004 had been detected in 48 U.S. states, the District of Columbia, and seven Canadian provinces (Nova Scotia, New Brunswick, Quebec, Ontario, Manitoba, Saskatchewan, and Alberta)².

1999	2000		2001
2002		2003
2004
		Figure 1. West Nile virus activity 1999-2004. © USGS and CDC. Click for larger view.

The anticipated spread of WNV beyond North America is well underway: it has been detected in several northern and eastern states in Mexico³, and in the Dominican Republic⁴, Jamaica⁵, Guadeloupe⁶, El Salvador⁷, Puerto Rico⁸, Belize⁹, Trinidad¹⁰, and Cuba¹⁰. Its spread to Hawaii and countries in South America is presumably only a matter of time.

On these pages, we have compiled current information on the various pieces of the puzzle, and provide it mostly in the form of answers to "frequently asked questions." Our “What’s New” section includes recent updates in the effort to document and understand the ramifications of the WNV phenomenon. We offer suggestions for rational, safe responses to an admittedly worrisome phenomenon (“What You Can Do”), including our 2-page summary of “The Basics,” for display or distribution. We also provide links to other sites with current West Nile virus information (“Some Additional Resources”), including one with information available in twelve languages other than English, and two with healthy advice regarding mosquito control.

Links to the individual subjects, below, will take you to printable documents requiring Adobe Acrobat Reader 4.0 or higher. The crows pictured on these pages were members of a marked population in Stillwater, Oklahoma, under study since 1997. West Nile virus arrived in Stillwater in September 2002. Brief stories about the lives of some of the individuals accompany their pictures.

American Crow, photo by Carolee Caffrey. MH was two years old when WNV arrived in Stillwater, OK, in August 2002. She was still living with her parents, along with two sisters (one older and one younger) and a three year old male that had moved in from next door the previous spring. MH died soon after WNV hit, and her younger sister and the immigrant male disappeared Her older sister moved out, and in with another family, to replace their missing female breeder. Her mother and father both survived the 2002 WNV season but disappeared in that of 2003, as did her older sister and her new family.

The Virus - information on viruses in general, West Nile virus in particular, the range of animals it has infected, transmission routes, and the availability of vaccines.

The Vectors - basic mosquito biology, as well as information about the mosquitoes that serve as vectors for West Nile virus.

The Victims - information on the different animal responses to being bitten by an infected mosquito.

Effects on Wildlife - information on what we know and what we don't know about the impacts of West Nile virus on our native wildlife.

What You Can Do - on keeping things in perspective, limiting mosquito breeding opportunities, avoiding being bitten, protecting your pets and local bird life, and what to do if you find a dead bird. Our 2-page “The Basics,” for display or distribution, summarizes much of this information.

Some Additional Resources - links to, and information on, other resources for information on West Nile virus.

We will continually update the pages here, as information becomes available through our own monitoring programs and from other sources. Please check back!

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Last update: 6/16/2005