Download West Nile Virus

West Nile Virus
Presented by Joyce and Isabel
History of the West Nile Virus
●
●
●
●
First isolated in West Nile District, Uganda in 1937 from a feverish woman
Studies conducted in Egypt in the 1950’s noted that the severity of the symptoms depended on the prevalence of the
disease.
In 1999, the first cases of WNV began to emerge in North American
○ In August of 1999, a small number of severe encephalitis cases were reported in Queens, New York.
■ These cases were not originally thought to be related to WNV, instead a common Eastern U.S,
Anthropod-borne viral encephalitis
■ After noticing a large number of dead birds with no noted avian pathogen, genomic tests were
conducted on area mosquitos, birds, brain matter from a human patient that died from encephelitis, and
a number of serological sample from suspected human patients confirmed the pathogen was WNV
■ By the end of the summer in 1999, 62 cases of WNV had been serologically confirmed in the Northeast
region of the U.S.
By 2002, WNV had spread to the west coast
Notable Outbreaks
In 1957, an outbreak of WNV in an Israeli nursing home led to the first record of the rare, severe neurological effects in
humans.
A 1962 outbreak in france and a 1974 outbreak in South Africa had some patients were recognized as developing
meningitis or encephalitis while many others simply developed mild febrile effects.
Through the 70’s and 80’s, few large outbreaks were reported
In 1996, an outbreak of WNV in Buchurest, Romania led to the conclusion that the epidemiology of WNV had changed
causing higher instances of CNS infection.
Following the Romanian outbreak, several outbreaks across Europe, Asia, and the Middle East displayed relatively
higher case of CNS infections than previous outbreaks.
A 1999 outbreak in Russia that involved 183 serologically confirmed cases including 84 cases of
meningoencephalitis that resulted in 40 fatalities
WNV Case Study
Patient Medical History:
An 81-year-old man with a history of hypertension, diabetes, atrial flutter, and sick sinus syndrome
Duration of stay:
33 days (15 in ICU)
Symptoms:
fever, chills, rigors, myalgia, worsening hand tremors, lower extremity weakness, and difficulty in walking.
Background:
-Two weeks prior, he was feeling well and went hiking.
-Two days prior to admission, family members noted a progressive change in his mental status.
Diagnosis:
-Abnormally High Protein levels
-Abnormally High levels of neutrophils
-Revealed Negative Gram stain.
- CSF tests were negative for varicella, herpes, syphilis, Epstein-Barr virus, Cytomegalovirus, and Cryptococcus so it was
Treatment & Recovery Timeline:
*Patient was treated for bacterial and viral meningitis with acyclovir, ceftriaxone, ampicillin, and vancomycin. Blood and CSF cultures were negative.
*The patient continued to have fever, rigors, and declining mental status. Additionally, the motor impairment progressed to involve the upper
extremities.
DAY 5: transferred to the ICU due to respiratory distress. Health-care-associated pneumonia was diagnosed and treated accordingly.
DAY 7: CSF serology revealed positive WNV
DAY 14: Worsening mental condition accompanied by upper gastrointestinal bleeding.
*The patient gradually improved and was discharged with residual upper and lower extremities paresis. Overall, the patient was hospitalized for 33
days including 15 days in the ICU.
Virulence Factors of West Nile Virus
The West Nile Virus is spherical and has a single-stranded DNA. It falls under the flavivirus category.
Flaviviruses are found in arthropods like mosquitoes and ticks which then infect the human.
These viruses cause encephalitis and other hemorrhagic diseases.
VIrulence factors specific to WNV:
-Capsid Protein binds and protects viral RNA
-Premembrane helps fold the envelope protein into correct shape (prevents premature fusion)
-Specialized molecules help attach onto cells
-Ability to respond to pH (Conforms shape of envelope in response to pH which causes fusion and the release of
genetic info into cytoplasm)
Environmental factors that aid in pathogenicity
● Global warming allows perfect conditions for mosquitoes (warm/humid)
● No vaccine for WNV
● arrangement of envelope proteins on the surface of the virus
● There are two main strains on different hemispheres on earth that allow for better spread
● The human body is incapable of building any kind of resistance before acquiring the virus
Description of Illness, Physiological Effect, Outward
Symptoms, and Incubation Period
80% of WNV infections are asymptomatic
20% of WNV infections show flu-like symptoms
>1% of WNV infections cause severe neuroinvasive disease
Physiological effects include…
●
●
●
●
●
●
●
●
acute onset of fever
Headache
Fatigue
Malaise
muscle pain
Weakness
gastrointestinal symptoms
transient macular rash on the trunk and extremities
Incubation period: 7-14 days
Mode of Transmission
Diagnostic Process
Testing methods for WNV:
● Commonly, WNV is test for by looking at IgM antibodies
specific to WNV within a cerebrospinal fluid sample
● Another way of detecting WNV is by testing for certain
sections of viral RNA specific to WNV
Treatment and Prevention Methods
Treatment
● There is currently no vaccine for WNV
● In mild cases, OTC pain killers can be used to treat fever
● In severe cases, patients may require hospital support (IV fluids
and stronger pain killers
Prevention
● The best preventative measure that can be taken against WNV is
to shield oneself from mosquitos.
Number of Case per Year in U.S. and Oregon
Number of Case per Year in U.S. and Oregon
References:
Flores Anticona, E. M., Zainah, H., Ouellette, D. R., & Johnson, L. E. (2012). Two case reports of neuroinvasive west nile
virus infection in the critical care unit. Case reports in infectious diseases, 2012.
Hayes EB, Sejvar JJ, Zaki SR, Lanciotti RS, Bode AV, Campbell GL. Virology, pathology, and clinical manifestations of
West Nile Virus disease. Emerg Infect Dis. 2016 July 8.
Samuel, M. A., & Diamond, M. S. (2006). Pathogenesis of West Nile Virus infection: a balance between virulence, innate
and adaptive immunity, and viral evasion. Journal of virology, 80(19), 9349-9360.
Sejvar, J. J. (2003). West Nile virus: An historical overview. The Ochsner Journal, 5(3),
6-10.