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Section 3. Summaries of Infectious Diseases
West Nile Virus
Clinical Manifestations
Etiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures
CLINICAL MANIFESTATIONS: The majority of infections attributable
to West Nile virus (WNV) are asymptomatic. Approximately 20%
of infected people will develop a self-limited febrile illness
called West Nile fever (WNF), and fewer than 1% will develop
neuroinvasive disease, such as aseptic meningitis, encephalitis,
or flaccid paralysis. The risk of neuroinvasive disease increases
with age and is highest among adults older than 60 years of
age. Patients with WNF typically have an abrupt onset of fever,
headache, myalgia, weakness, and often, abdominal pain, nausea,
vomiting, or diarrhea. Some patients have a transient maculopapular
rash. The acute phase of illness usually resolves within several
days, but fatigue, malaise, and weakness can linger for weeks.
Patients with neuroinvasive disease may present with neck stiffness
and headache typical of aseptic meningitis, mental status changes
indicating encephalitis, movement disorders such as tremor or
Parkinsonism, seizures, or acute flaccid paralysis with or without
meningitis or encephalitis. Isolated limb paralysis can occur
without fever or apparent viral prodrome. Flaccid paralysis
caused by WNV infection is similar clinically and pathologically
to poliomyelitis caused by poliovirus, with damage of anterior
horn cells, and may progress to respiratory muscle paralysis
requiring mechanical ventilation. Guillain-Barré syndrome
also may occur after WNV infection and can be distinguished
from anterior horn cell damage by clinical manifestations and
electrophysiologic testing. Cardiac dysrhythmias, myocarditis,
rhabdomyolysis, optic neuritis, uveitis, chorioretinitis, orchitis,
pancreatitis, and hepatitis have been described rarely after
WNV infection.
Most women known to have been infected with WNV during pregnancy have delivered infants without evidence of infection or clinical abnormalities. In the single known instance of confirmed congenital WNV infection, the mother developed WNV encephalitis during the 27th week of gestation, . . . [Go to Full Text]
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