West Nile Virus (WNV) is an arborovirus or insect borne infection.
It has a 3 -15 day incubation period with viraemia on days 4-8.
Symptoms can be none to meningitis or encephalitis. The mean age
of those affected is 65 yrs. It is more severe with advancing age.
Potential cause for the New York outbreak migratory birds (unlikely),
imported birds, infected humans, imported mosquitoes, or bioterrorism
Seventy- eight bird species will carry the WNV. In 2000 there were
21 human cases (fatalities of 11%.) West Nile Virus has occurred
in France, Israel, and Russia.
West Nile virus is transmitted through the bite of a mosquito, which
has become infected with virus by feeding on an infected bird.
Infections with WNV are usually mild or unapparent. Symptoms can
range from a slight fever and mild headache to the acute onset of
severe headache, high fever, stiff neck, muscle weakness, focal
neurological signs, and disorientation with alterations in the level
of consciousness, and death.
Symptoms could begin 3 to 12 days following the bite of an infected
mosquito. In the New York outbreak, the elderly tended to be at
risk for more serious forms of the disease. Travel to endemic areas
should be considered when individuals present with the above symptoms.
Role of the Physician:
If you should see patients where you suspect encephalitis, please
order 2 blood samples, 3 weeks apart (acute and convalescent blood
samples) for antibody titres. For cerebrospinal fluid (CSF) specimens,
send 1to 2 cc on ice for the presence of antibody, and WNV by polymerase
chain reaction (PCR) and also include one blood sample (10 cc for
adults; 1 to 2 cc for young children). For brain biopsy specimens,
in a sterile container on crushed ice, not formalin fixed specimens.
Nile Virus links
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