West nile virus history and symptoms

History and Symptoms
WNV has three different effects on humans. The first is an asymptomatic infection; the second is a mild febrile syndrome termed West Nile Fever; the third is a neuroinvasive disease termed West Nile meningitis or encephalitis. In infected individuals the ratio between the three states is roughly 110:30:1.

The second, febrile stage has an incubation period of 3-8 days followed by fever, headache, chills, diaphoresis, weakness, lymphadenopathy, and drowsiness. Occasionally there is a short-lived truncal rash and some patients experience gastrointestinal symptoms including nausea, vomiting, loss of appetite, or diarrhea. All symptoms are resolved within 7-10 days, although fatigue can last for some weeks and lymphadenopathy can take up to two months to resolve.

The more dangerous encephalitis is characterized by similar early symptoms but also a decreased level of consciousness, sometimes approaching near-coma. Deep tendon reflexes are hyperactive at first, later diminished. There are also extrapyramidal disorders. Recovery is marked by a long convalescence with fatigue.

More recent outbreaks have resulted in a deeper study of the disease and other, rarer, outcomes have been identified.The spinal cord may be infected, marked by anterior myelitis with or without encephalitis. WNV-associated Guillain-Barré syndrome has been identified and other rare effects include multifocal chorioretinitis (which has 100% specificity for identifying WNV infection in patients with possible WNV encephalitis) hepatitis, myocarditis, nephritis, pancreatitis, and splenomegaly.