Lecture 16: West Nile Virus

To which virus family does West Nile Virus belong?

Flaviviridae

What is the genetic structure of the West Nile Virus?

Enveloped, single-stranded RNA virus

What are the primary vectors for West Nile Virus?

Mosquitoes, specifically of the genus Culex

What is the principal animal reservoir for West Nile Virus?

Birds

Besides mosquitoes, what are three alternative modes of transmission for West Nile Virus?

Blood transfusions, transplacental transmission, and breast feeding

In what year was West Nile Virus first isolated?

1937

Where was West Nile Virus first isolated?

West Nile province of Uganda

What major 1999 outbreak signaled the arrival of West Nile Virus in the United States?

An encephalitis outbreak in Queens, New York

What is the typical pathogenesis of West Nile Virus after a mosquito bite?

Replication in dendritic cells, spread to regional lymph nodes, entry into the blood, and invasion of neural tissue

What percentage of West Nile Virus infections are asymptomatic?

Approximately 80%

What is the typical incubation period for West Nile fever?

2 to 14 days

What are the common clinical signs of West Nile fever?

Fever, headache, malaise, myalgia, skin rash, lymphadenopathy, vomiting, and diarrhea

What clinical signs characterize West Nile meningitis?

Fever, headache, stiff neck, nuchal rigidity, photophobia, and positive Kernig's and Brudzinski's signs

How does West Nile encephalitis differ from West Nile meningitis?

Encephalitis involves the brain parenchyma, leading to altered consciousness, disorientation, and focal neurological symptoms

Which part of the nervous system is selectively invaded in acute flaccid paralysis caused by West Nile Virus?

Spinal anterior horns (motor neurons)

What is the primary diagnostic method for West Nile Virus?

Serology measuring IgM antibody levels via ELISA

What constitutes a positive result in a paired serum titer test for West Nile Virus?

A four-fold increase in antibody titer between two samples taken two weeks apart

What diagnostic tools can help locate lesions in cases of West Nile-induced flaccid paralysis?

Electrophysiological studies, such as EMG

What is the current status of antiviral therapy for West Nile Virus?

No antiviral therapy has shown significant effectiveness

What experimental therapy has been tested for neural forms of West Nile Virus?

Interferon (IFN)

What is the primary treatment approach for West Nile Virus patients?

Supportive therapy, including fluid replacement and symptomatic treatment

What are the main prevention strategies for West Nile Virus?

Avoiding mosquito bites by using insecticide and wearing long clothing

Which two species are considered the most important reservoirs for West Nile Virus?

Humans and horses