West Nile virus is one of the many members of the genus Flavivirus that are known to cause human disease. It has been reported in Africa, Asia, Europe, the Middle East, and North America. West Nile virus causes serious manifestations in approximately 1% of persons who are infected, with increased morbidity and mortality in individuals older than 50 years. Individuals older than 60 years are at particular risk.
Mosquito bites may or may not be present in an infected person. A history of travel to or from an area that is known to harbor the virus is common. Symptoms of mild infection may last 3-6 days and may include fever. Other symptoms include nausea, anorexia, malaise, myalgia, headache, backache, rash, eye pain, and vomiting. Symptoms of more severe illness include severe muscle weakness, flaccid paralysis or increased muscle spasticity, photophobia, seizures, mental status changes, respiratory symptoms, and an erythematous, maculopapular, or morbilliform rash involving the neck, trunk, arms, or legs.
Signs of encephalitis and meningoencephalitis may be seen. These include mental status changes such as confusion, stupor, or coma. Other findings include positive Brudzinski and Kernig signs, papilledema, cranial nerve involvement (eg, facial weakness, double vision, visual loss, decreased taste sensation), motor strength weakness, decreased sensation, hyperreflexia, and positive pathologic reflexes (eg, Babinski sign, Hoffman sign).
Serologic testing to detect IgM antibodies is currently the best means of diagnosing West Nile virus infection. According to guidelines from the Centers for Disease Control and Prevention (CDC), however, if serum is collected within 8 days of illness onset, the absence of detectable virus-specific IgM does not exclude the diagnosis of West Nile virus. CDC also states that although viral cultures and tests to detect viral RNA (eg, RT-PCR) can be performed on serum, cerebrospinal fluid, and tissue specimens to help confirm an infection early in the course of illness, negative results do not rule out West Nile virus infection.
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Cite this: Michael Stuart Bronze. Fast Five Quiz: Mosquito-Borne Diseases - Medscape - May 06, 2020.