West Nile Virus: Clinical Description (from CDC)
Severe Disease: West Nile Meningitis, West Nile Encephalitis, and West Nile Poliomyelitis
When the central nervous system (CNS) is affected, clinical syndromes ranging from febrile headache to aseptic meningitis to encephalitis may occur, and these are usually indistinguishable from similar syndromes caused by other viruses.
About 60% to 75% of people with neuroinvasive WNV infection reportedly have encephalitis or meningoencephalitis, which is characterized by altered mental status or focal neurologic findings.
About 25% to 35% of people with neuroinvasive WNV infection reportedly have meningitis without evidence of encephalitis.
Headache can be a prominent feature of WNV fever, meningitis, or encephalitis and is not a useful indicator of neuroinvasive disease.
West Nile meningitis usually involves fever, headache, and stiff neck. Pleocytosis is present. Changes in consciousness are not usually seen and are mild when present.
West Nile encephalitis, the most severe form of neuroinvasive West Nile viral disease, involves fever and headache, but there are more global symptoms. There is usually an alteration of consciousness, which may be mild and result in lethargy but may progress to confusion or coma. Focal neurologic deficits, including limb paralysis and cranial nerve palsies, may be observed. Tremors and movement disorders also have been noted.
West Nile poliomyelitis, a flaccid paralysis syndrome associated with WNV infection, is less common than meningitis or encephalitis. This syndrome is generally characterized by the acute onset of asymmetric limb weakness or paralysis in the absence of sensory loss. Pain sometimes precedes the paralysis. The paralysis can occur in the absence of fever, headache, or other common symptoms associated with WNV infection. Involvement of respiratory muscles, leading to acute respiratory failure, can sometimes occur. For more information, see Q & A: WNV Poliomyelitis.
Clinical Features of Severe Disease
Ataxia and extrapyramidal signs
Change in mental status
A minority of patients with severe disease develop a maculopapular or morbilliform rash involving the neck, trunk, arms, or legs.
Flaccid paralysis is sometimes seen.
Although not observed in recent outbreaks, myocarditis, pancreatitis, and fulminant hepatitis have been described.
Severe disease laboratory findings next >>