West Nile Fever
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West Nile Fever

West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall.

Signs And Symptoms
80% of those infected with WNV will be asymptomatic. 20% of those infected develop symptoms that can last from a few days to several weeks and can include:
  • Fever
  • Headache
  • Generalised body aches
  • Nausea and vomiting
  • Swollen lymph glands
  • Rash over the chest, abdomen and back 

Less frequently the virus can affect the nervous system causing encephalitis, meningitis or poliomyelitis. These present with nausea, vomiting, diarrhoea, high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

Incubation Period
Usually 3-14 days.

Mode of transmission

WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Rarely, WNV can be spread through blood transfusions, organ transplants, breastfeeding and during pregnancy from mother to baby. It is not spread through casual person-to-person contact.

Diagnostic tests
The most efficient diagnostic method is detection of IgM antibody against WNV in serum collected within 8 to 14 days of illness onset or cerebrospinal fluid collected within 8 days of illness onset.

There is no specific treatment for WNV infection. In cases with milder symptoms, people experience symptoms such as fever and aches that pass on their own. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing and nursing care.

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