West Nile Virus

Question 1

Leading cause of domestically acquired arboviral disease in the U.S

Answer 1

West Nile Virus

Question 2

Predisposing factors for West Nile Virus

Answer 2

Outdoor activities during spring & summer; mosquito bites

Question 3

How is West Nile Virus transmitted

Answer 3

• Culexmosquito
• blood transfusion/organ donation
• mother to child

Question 4

Incubation period for West NIle Virus

Answer 4

2 - 6 days, but can range from 2 - 14 days

Question 5

What time of year do outbreaks of West NIle Virus occur

Answer 5

between mid-July and early September

Question 6

How does elevated temperatures and rainfall correlate with WNV transmission

Answer 6

• Elevated temperatures & rainfall correlate with increased WNV transmission & infection.
• The warmer & hotter it is, the more mosquitos will breed

Question 7

How is WNV transmitted from person-to-person

Answer 7

usually related to blood transfusion and organ transplantation.

Question 8

How do mosquitoes become infected with WNV

Answer 8

Mosquitoes become infected when they feed on infected birds; then spread virus to humans & other animals during blood meals.

Question 9

Horses and humans are considered what kind of host for WNV

Answer 9

Horses & humans are considered ‘dead-end’ hosts

Question 10

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.

Answer 10

West Nile Virus

Question 11

What percentage of WNV infections are subclinical or asymptomatic

Answer 11

70-80%

Question 12

What percentage of WNV develop neuroinvasive WNV

Answer 12

<1%

Question 13

How does neuroinvasive WNV manifest

Answer 13

• WNV Meningitis
• WNV Encephalitis
• WNV Acute Flaccid Paralysis

Question 14

Clinically indistinguishable from viral meningitis due to other etiologies & typically presents with fever, headache, and nuchal rigidity.

Answer 14

WNV Meningitis

Question 15

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.

Answer 15

WNV Encephalitis

Question 16

• 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.

Answer 16

WNV Acute Flaccid Paralysis:

Question 17

Lab Dx of WNV

Answer 17

• ELISA is used to detect IgM antibody in serum
• If CNS symptoms are present, lumbar puncture with CSF analysis

Question 18

Is CBC a reliable indicator for WNV

Answer 18

No

Question 19

Treatment of West Nile Virus

Answer 19

• no specific treatment
• supportive measures

Question 20

When is MEDEVAC warranted for WNV

Answer 20

MEDEVAC is warranted if there are signs of encephalitis, meningitis, or paralysis.

Question 21

Prevention of WNV

Answer 21

• Community-level mosquito control programs to reduce vector densities.
• Personal protective measures to decrease exposure to infected mosquitoes
• Screening of blood and organ donors.

Question 22

Disposition for non-neuroinvasive and neuroinvasive WNV

Answer 22

• 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