U.S. Department of the Interior

U.S. Geological Survey

Factsheet 2004-3002

August 2003

USGS West Nile Virus 

Research Strategy

This plan integrates science across multiple USGS disciplines, and provides national 

and international opportunities for USGS 

collaboration with state and federal agencies, 

academic institutions, and non-governmental 

organizations throughout the Americas. 

In 2002, West Nile virus, a mosquitoborne virus in the Flavivirus family, 

was detected in 44 states, 5 Canadian 

provinces, the District of Columbia, 

and Northeastern Mexico. In 2003, the 

virus was found in at least 44 states 

and 6 Canadian provinces. Scientists 

suspect the disease will be detected in 

every state in the continental U.S., and 

possibly Alaska and Hawaii by the end 

of 2003. WNV has also spread into 

Central America and the Caribbean. The 

disease was detected in birds and horses 

in Mexico and horses in El Salvador. In 

addition, researchers detected antibodies 

to WNV in non-migratory birds in 

the Dominican Republic and Jamaica, 

suggesting local transmission of the 

virus on these islands.

The increase in the geographic host 

range of the virus coincides with a 

dramatic increase in the distribution 

and number of North American wildlife 

species infected. Over 160 bird, 18 

mammal and one reptile species are 

known to be susceptible to WNV. 

Wildlife officials are concerned about 

the effects WNV has on all susceptible 

wildlife species, especially wild 

bird populations and threatened and 

endangered species. A sharp increase 

in mortality of some bird populations, 

coinciding with the appearance of WNV, 

led to several collaborative efforts to 

investigate the impact of the virus on 

these bird populations.

Scientists are conducting research on 

the susceptibility and pathology of 

WNV in native wildlife species, and 

are investigating the range and role of 

wildlife species as disease reservoirs for 

other wildlife, domestic animals, and 

humans. While research is beginning to 

generate results, much about the virus 

remains unknown. 

Current research

Scientists suspect bird migrations in 

the spring and fall play an important 

role in the wide dissemination of WNV 

throughout North America and may 

eventually play a role in the disease’s 

spread throughout much of the Western 

Hemisphere. For the third year, U.S. 

Geological Survey (USGS) scientists are 

surveying and collecting blood samples 

for WNV testing from migrating wild 

birds along the Atlantic and Mississippi 

migratory flyways. Over 10,000 birds 

from 142 different species were caught, 

sampled, and released at 23 national 

wildlife sites at U.S. Fish and Wildlife 

Service refuges, National Parks, and 

military facilities in 12 states since 2001.

Results are still pending, but initial 

information indicates 2 percent of gray 

catbirds, northern cardinals, American 

robins, blue jays and brown thrashers 

sampled in 2001 and 2002 were 

antibody positive for WNV, indicating 

they had been previously exposed to 

the virus. USGS is collaborating on 

this study with the Centers for Disease 

Control and Prevention (CDC), where 

scientists are examining the distribution 

and number of mosquito species in 

relation to avian mortality, weather, and 

land cover.

Researchers believe this study will 

provide basic information on the 

distribution and spread of the virus. 

USGS scientists will combine these data 

with information about avian migratory 

patterns, landscape characteristics and 

weather conditions over space and 

time, providing a foundation for the 

development of models to forecast the 

risk of human illness.

Red-shouldered hawk

Photo courtesy of Milton Friend, USGS

Blue jay sampled for WNV testing

Photo courtesy of Robert J. Dusek, USGS
For more information on the West Nile Virus 

research strategy, please contact Dr. Gregory 

Smith, USGS, (703) 648-4071, Dr. Christoper 

Brand, USGS, (608) 270-2440, or Dr. Emi 

Saito, USGS, (608) 270-2456.

USGS scientists studied the 

susceptibility of crows, mallards 

and cranes to WNV infection, and 

are planning disease susceptibility 

studies with vector biologists from 

the University of Wisconsin to 

experimentally determine the ways virus 

infects various bird species, particularly 

waterfowl, raptors, sandhill cranes, 

and amakihi, a native Hawaiian bird. 

Investigators in the USGS Biological 

Safety Level-3 containment laboratory 

will also study how birds develop 

resistance to WNV that enables them to 

successfully fend off the viral attack. In 

2003, USGS scientists will also begin 

to investigate the effects of WNV on 

American kestrel populations.

In addition to research and surveillance 

activities, USGS will continue to 

investigate avian wildlife mortality 

events such as those occurring among 

raptors and American white pelicans. In 

2002, USGS wildlife disease specialists 

at the National Wildlife Health Center 

determined the virus played a role in 

avian mortality throughout the U.S. The 

disease is linked to large-scale raptor 

mortalities throughout Eastern and 

Midwestern states, and possibly pelican 

mortality in the Midwest. 

Photos courtesy of Robert J. Dusek, USGS, except crow, courtesy Dan Sudia

A variety of avian and mammalian 

species are susceptible to West 

Nile virus

Current USGS/CDC collaborative maps 

detailing WNV activity can be found at 

http://westnilemaps.usgs.gov/. 

Current lists of WNV-positive species can 

be found at http://www.nwhc.usgs.gov/

research/west_nile/wnvaffected.html/

These, and additional field and 

laboratory studies being planned, will 

provide a comprehensive and integrated 

research approach to answer critical 

questions about West Nile virus that will 

ultimately benefit wildlife, public health 

and domestic animal health.