West Nile Virus Flashcards
Leading cause of domestically acquired arboviral disease in the U.S
West Nile Virus
Predisposing factors for West Nile Virus
Outdoor activities during spring & summer; mosquito bites
How is West Nile Virus transmitted
- Culexmosquito
- blood transfusion/organ donation
- mother to child
Incubation period for West NIle Virus
2 - 6 days, but can range from 2 - 14 days
What time of year do outbreaks of West NIle Virus occur
between mid-July and early September
How does elevated temperatures and rainfall correlate with WNV transmission
- Elevated temperatures & rainfall correlate with increased WNV transmission & infection.
- The warmer & hotter it is, the more mosquitos will breed
How is WNV transmitted from person-to-person
usually related to blood transfusion and organ transplantation.
How do mosquitoes become infected with WNV
Mosquitoes become infected when they feed on infected birds; then spread virus to humans & other animals during blood meals.
Horses and humans are considered what kind of host for WNV
Horses & humans are considered ‘dead-end’ hosts
Presentation:
- Febrile patient
- Headache, weakness, myalgia, or arthralgia
- Gastrointestinal symptoms
- Transient maculopapular rash
- Acute neurologic illness
- Recent exposure to mosquitoes during the summer months in endemic areas.
West Nile Virus
What percentage of WNV infections are subclinical or asymptomatic
70-80%
What percentage of WNV develop neuroinvasive WNV
<1%
How does neuroinvasive WNV manifest
- WNV Meningitis
- WNV Encephalitis
- WNV Acute Flaccid Paralysis
Clinically indistinguishable from viral meningitis due to other etiologies & typically presents with fever, headache, and nuchal rigidity.
WNV Meningitis
A more severe clinical syndrome that usually manifests with fever and altered mental status, seizures, focal neurologic deficits, or movement disorders such as tremor or Parkinsonism.
WNV Encephalitis
- Typically, clinical & pathologically identical to poliovirus associated poliomyelitis and may progress to respiratory paralysis requiring mechanical ventilation.
- Often presents as isolated limb paresis or
paralysis and can occur without fever or apparent viral prodrome.
WNV Acute Flaccid Paralysis:
Lab Dx of WNV
- ELISA is used to detect IgM antibody in serum
- If CNS symptoms are present, lumbar puncture with CSF analysis
Is CBC a reliable indicator for WNV
No
Treatment of West Nile Virus
- no specific treatment
- supportive measures
When is MEDEVAC warranted for WNV
MEDEVAC is warranted if there are signs of encephalitis, meningitis, or paralysis.
Prevention of WNV
- Community-level mosquito control programs to reduce vector densities.
- Personal protective measures to decrease exposure to infected mosquitoes
- Screening of blood and organ donors.
Disposition for non-neuroinvasive and neuroinvasive WNV
- non-neuroinvasive WNV disease recover completely; however, fatigue, malaise, and weakness can linger for weeks or months.
- Patients who recover from WNV encephalitis or
poliomyelitis often have residual neurologic deficits
