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West Nile Virus
BY C I N D Y R A M E Y
West Nile Virus
 West Nile virus (WNV) is a mosquito-borne zoonotic
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arbovirus
Family: Flaviviridae
Genus: Flavivirus Japanese Encephalitis Antigenic
Complex
Size: 40-60nm
Incubation period: ranges from three to 14 days
West Nile Virus
 West Nile Virus was first isolated in the West Nile
district of Uganda in 1937
 It first appeared in North America in 1999
 The virus first was reported in Oregon in 1999
 When it re-surfaced three years ago in 2009, a total
of 12 cases were reported
Transmission of West Nile Virus
 Most West Nile virus infections occur during warm
weather, when mosquito populations are active
 Infectious mosquitoes carry virus particles in their
salivary glands and infect susceptible bird species
during blood-meal feeding
 The bite of an infected mosquito infects human hosts
Transmission of West Nile Virus Cont.
Risk Factors
 Age. Adults over the age of 50 are at higher risk of
infection.
 Health. Those who have a weakened immune
system, such as from receiving an organ transplant,
are at greater risk of infection.
Signs and Symptoms
 Most people who are infected with West Nile Virus
show no signs or symptoms
 Some develop a life-threatening illness that includes
inflammation of the brain (encephalitits)
 Mild signs and symptoms of a West Nile virus
infection generally go away on their own
 But severe signs and symptoms — such as a severe
headache, disorientation or sudden weakness —
require immediate attention
Mild Signs and Symptoms Include
 Fever
 Headache
 Body aches
 Fatigue
 Skin rash (occasionally)
 Swollen lymph glands (occasionally)
 Eye pain (occasionally)
Severe Signs and Symptoms Include
 High fever
 Severe headache
 Stiff neck
 Disorientation or confusion
 Stupor or coma
 Tremors or muscle jerking
 Lack of coordination
 Convulsions
 Pain
 Partial paralysis or sudden weakness
Prevention of West Nile Virus
 Avoid areas where West Nile Virus is common
 Use mosquito repellent
 Wear clothing that covers your skin
 Avoid areas of stagnant water
Interesting Factoids
 West Nile virus has been detected in dead birds of at
least 326 species
Diagnosis of West Nile Virus
Laboratory tests
 If you are infected, a blood test may show a rising
level of antibodies to the West Nile virus
 A positive ribonucleic acid (RNA) test for the West
Nile virus also is an indicator that you have the virus
Diagnosis of West Nile Virus Cont.
Lumbar puncture (spinal tap)
 The most common way to diagnose West Nile Virus
is to analyze the cerebrospinal fluid surrounding your
brain and spinal cord
 A needle inserted between the lower vertebrae of
your spine is used to extract a sample of fluid for
laboratory analysis
Brain tests
 In some cases, an electroencephalography (EEG) or
an MRI scan can help detect brain inflammation
Treatment of West Nile Virus
Supportive therapy
 Most people recover from West Nile virus without
treatment
 Over-the-counter pain relievers can help ease mild
headaches and muscle pain
 Supportive therapy in a hospital with intravenous
fluids and medicines may prevent other types of
infections
Treatment of West Nile Virus Cont.
Interferon therapy
 An experimental type of immune cell therapy as a
treatment for encephalitis caused by West Nile virus
 Some research shows that people who receive
interferon may recover better than those who don't
receive the drug, but more study is needed
West Nile Virus Case Study October 23, 2012
 As of October 23, 2012, 48 states have reported
West Nile virus infections in people, birds, or
mosquitoes
4,725 cases
 219 deaths
 2,413 (51%) were classified as neuroinvasive disease (such
as meningitis or encephalitis)
 2,312 (49%) were classified as non-neuroinvasive disease

West Nile Virus Case Study October 23, 2012
 Almost 70 percent of the cases have been reported
from eight states

Texas, California, Louisiana, Mississippi, Illinois, South
Dakota, Michigan, and Oklahoma
 Over a third of all cases have been reported from
Texas.
Cases of West Nile Virus in Oregon
 According to the CDC Oregon has had a mere 3 cases
of West Nile Virus in 2012. None of these
documented cases were neuroinvasive and no deaths
have been reported. However, that is an increase
from 2011 where no cases were reported. Other
states have not been so fortunate. Although the cases
in Oregon are minimal compared to those in other
states, West Nile Virus is still very much a concern
and precautions should always be taken to prevent
infection.
Importance of Studying West Nile Virus
 West Nile Virus has become more common since the
spread of the disease to the United States in 1999.
The recent epidemic is proof that the disease is very
real and can be life threatening. Understanding the
disease, how to prevent it, and what signs and
symptoms to look for will make sure that you do not
become a statistic of this serious virus.
Websites
 http://www.mayoclinic.com/health/west-nile-
virus/DS00438
 http://www.cdc.gov/ncidod/dvbid/westnile/cycle.ht
m
 http://abcnews.go.com/Health/west-nile-virusdoctors-fight-largest-outbreakus/story?id=17254382#.UI8mZ2dNKSo
 http://en.wikipedia.org/wiki/West_Nile_virus