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What are the symptoms of West Nile virus (WNV) infection?
A. Infection with WNV can be asymptomtic
(no symptoms), or can lead to West Nile fever
or severe West Nile disease.
is estimated that about 20% of people who become infected
with WNV will develop West Nile fever.
Symptoms include fever, headache, tiredness, and body aches,
occasionally with a skin rash (on the trunk of the body)
and swollen lymph glands. While the illness can be as short
as a few days, even healthy people have reported being sick
for several weeks.
symptoms of severe disease (also called
neuroinvasive disease, such as West
Nile encephalitis or meningitis
or West Nile poliomyelitis) include headache,
high fever, neck stiffness, stupor, disorientation, coma,
tremors, convulsions, muscle weakness, and paralysis. It
is estimated that approximately 1 in 150 persons infected
with the West Nile virus will develop a more severe form
of disease. Serious illness can occur in people of any age,
however people over age 50 and some immunocompromised persons
(for example, transplant patients) are at the highest risk
for getting severely ill when infected with WNV.
people (about 4 out of 5) who are infected with West
Nile virus will not develop any type of illness (an asymptomatic
infection), however you cannot know ahead of time if you'll
get sick or not when infected.
What is the incubation period in humans (i.e., time from
infection to onset of disease symptoms) for West Nile disease?
A. Usually 2 to 15 days.
How long do symptoms last?
A. Symptoms of West Nile fever will
generally last a few days, although even some healthy people
report having the illness last for several weeks. The symptoms
of severe disease (encephalitis or meningitis) may last
several weeks, although neurological effects may be permanent.
What is meant by West Nile encephalitis, West Nile meningitis,
West Nile poliomyelitis, “neuroinvasive disease” and West
The most severe type of disease due to a person
being infected with West Nile virus is sometimes called
“neuroinvasive disease,” because it affects a person's nervous
system. Specific types of neuroinvasive disease include:
West Nile encephalitis, West Nile meningitis, West Nile
meningoencephalitis and West Nile poliomyelitis. Encephalitis
refers to an inflammation of the brain, meningitis is an
inflammation of the membrane around the brain and the spinal
cord, meningoencephalitis refers to inflammation of the
brain and the membrane surrounding it, and poliomyelitis
refers to an inflammation of the spinal cord.
Nile Fever is another type of illness that can occur in
people who become infected with the virus. It is characterized
by fever, headache, tiredness, aches and sometimes rash.
Although the illness can be as short as a few days, even
healthy people have been sick for several weeks.
If I have West Nile Fever, can it turn into West
When someone is infected with West Nile virus (WNV) they
will typically have one of three outcomes: No symptoms (most
likely), West Nile fever (WNF in about 20% of people) or
severe West Nile disease, such as meningitis or encephalitis
(less than 1% of those who get infected). If you develop
a high fever with severe headache, consult your health care
Nile fever is characterized by symptoms such as fever, body
aches, headache and sometimes swollen lymph glands and rash.
West Nile fever generally lasts only a few days, though
in some cases symptoms have been reported to last longer,
even up to several weeks. West Nile fever does not appear
to cause any permanent health effects. There is no specific
treatment for WNV infection. People with West Nile fever
recover on their own, though symptoms can be relieved through
various treatments (such as medication for headache and
body aches, etc.).
people may develop a brief, WNF-like illness (early symptoms)
before they develop more severe disease, though the percentage
of patients in whom this occurs is not known.
an infected person may develop more severe disease such
as “West Nile encephalitis,” “West Nile
meningitis” or “West Nile meningoencephalitis.”
Encephalitis refers to an inflammation of the brain, meningitis
is an inflammation of the membrane around the brain and
the spinal cord, and meningoencephalitis refers to inflammation
of the brain and the membrane surrounding it. Although there
is no treatment for WNV infection itself, the person with
severe disease often needs to be hospitalized. Care may
involve nursing IV fluids, respiratory support, and prevention
of secondary infections.