virus blown across the Atlantic Ocean by high storm
winds; an accidental exposure from a U.S. govern-
ment animal disease center and germ laboratory on
Plum Island twenty miles east of North Fork; or an
undetected bioterrorism attack.
Facts About the Virus West Nile virus belongs to
a group of disease-causing viruses known as flavi-
viruses. Flaviviruses are spread by insects, usually
mosquitoes. Other diseases caused by flaviviruses
include yellow fever, dengue fever, and St. Louis en-
cephalitis. In most cases, humans infected with West
Nile virus are asymptomatic. In a small percentage
of cases, symptoms are more severe, including fe-
ver, body aches, swollen lymph glands, headaches,
and skin rash. If West Nile virus crosses the blood-
brain barrier, the disease becomes life-threatening.
A West Nile virus infection of the brain may result
in encephalitis—inflammation of the brain—or
meningitis—inflammation of the brain’s lining and
the spinal cord. Severe symptoms usually occur in
the elderly, young children, and those with compro-
mised immune systems. Of the fifty-nine patients in
New York City who suffered from encephalitis or
meningitis caused by the virus, seven (12 percent)
died. There are no antiviral drugs to treat West Nile
virus and no vaccines to prevent infection.
The first stage in the West Nile transmission cycle
occurs when a female mosquito bites an infected
bird. The virus circulates in the mosquito’s salivary
glands and is transmitted to humans and other ani-
mals when the mosquito bites to take a blood meal.
West Nile virus may also be spread via organ trans-
plants, blood transfusions, and infected breast milk.
More than one hundred species of birds in North
America have been identified as being infected with
West Nile virus, and while the vast majority of infec-
tions are in birds, the virus also maintains high infec-
tion rates in horses and has been isolated in bats,
cats, chipmunks, squirrels, rabbits, and skunks.
Impact The initial outbreak of West Nile virus in
New York City resulted in hysteria. Chemical spray-
ing for mosquitoes began on a massive scale despite
health worries regarding pesticides. Eventually,
more individuals would be admitted to area hospi-
tals suffering from symptoms of pesticide poisoning
than from West Nile virus. Towns instituted evening
curfews on outdoor activities. Parents were warned
to keep children indoors to avoid the chance of a
mosquito bite. Safety warnings were issued regard-
ing mosquito avoidance to people working out-
doors, campers, hunters, and anyone living near ar-
eas of standing water. Alerts were issued for people
who found dead birds to report the finds to local
health agencies for removal and testing.
When it was found that West Nile virus could
spread via blood transfusion, the American Red
Cross initiated new standards for blood testing. As
the vector for West Nile virus arriving in North
America is unknown, worries regarding threats of
bioterrorism increased. The spread of West Nile virus
began to be constantly monitored along routes of
migrating birds. In addition, warmer climatic con-
ditions resulting from global climate change are
expanding the range of mosquito populations,
bringing the threat of West Nile virus to new envi-
ronments. As the virus appears in environments har-
boring year-round mosquito populations, condi-
tions for a potential severe epidemic increase.
Subsequent Events By 2003, all but a handful of
states had reported human cases of the virus. In
2007, there were 3,623 cases and 124 West Nile-
related deaths reported to the CDC, a significant
drop from 2002, when 4,156 cases and 284 fatalities
were reported.
Further Reading
Lashley, Felissa R., and Jerry D. Durham, eds.
Emerging Infectious Diseases: Trends and Issues. New
York: Springer, 2002. An engaging account of the
1999 outbreak of West Nile virus in New York City.
Lee, M. C.West Nile Virus: Overview and Abstracts. New
York: Nova Science, 2003. An extensive collection
of abstracts and references on West Nile virus re-
search.
Levy, Elinor, and Mark Fischetti.The New Killer Dis-
eases: How the Alarming Evolution of Mutant Germs
Threatens Us All. New York: Crown, 2003. Contains
a detailed account of the original investigations
into the 1999 outbreak of West Nile virus.
White, Dennis J., and Dale L. Morse, eds.West Nile Vi-
rus: Detection, Surveillance, and Control.Annals of
The New York Academy of Sciences. New York:
New York Academy of Sciences, 2001. A good re-
source book covering the disease’s history and
epidemiology.
Randall L. MilsteinSee also Earth in the Balance; Global warming de-
bate; Health care; Medicine; Terrorism.The Nineties in America West Nile virus outbreak 913