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Back to Infectious Diseases
Infections
West Nile Virus
Tuesday, 1 July, 2003
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West Nile Virus can cause meningitis (inflammation
of the tissues covering the brain & spinal cord) & encephalitis (inflammation
of the brain). |
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West Nile virus seems to be a major health concern in the USA this summer.
So what is there to know about this virus?
West Nile virus belongs to a family of viruses called flavivirus. Although
most people infected with the virus more often get a fever that resolves
gradually, it can occasionally cause aseptic meningitis (inflammation of
the tissues covering the brain and spinal cord) and severe encephalitis
(inflammation of the brain); these serious infections are particularly common
among children and the elderly.
Why is it a concern?
The main reason for concern is that this virus is carried and transmitted
among wild birds and animals (including humans) by Culex mosquitoes.
Meaning, that spread of this dangerous virus can be very rapid in areas
where the Culex mosquitoes are common.
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The virus was more commonly found in Africa, the Middle East, southern
Europe, and Asia. In 1996 West Nile virus caused more than 300 cases of
CNS disease, with 10% mortality, in the Danube flood plain, including Bucharest.
In 1999 the virus appeared in New York City, causing more than 60 cases
of aseptic meningitis or encephalitis among humans as well as among crows,
exotic zoo birds, and other avians. Since then
it has spread rapidly to more than 40 states, infecting birds, humans and
horses. In addition, the virus has been implicated in severe and
fatal hepatic necrosis in some parts of Africa. In 2002, the Centers for
Disease Control and Prevention (CDC) reported more than 4,000 human infections
in the United States. The disease threatens to spread farther in the
Americas via bird migration.
What are the symptoms?
The Incubation Period of West Nile Virus is 3-6 days.
Common signs and symptoms of West Nile virus infection include:
- Fever
- Headache
- Muscle aches
- Backache
- A maculopapular skin rash
- Lymph gland enlargement
If the infection involves the brain (not common) the signs and symptoms
may also include:
- Severe headache
- Stiff neck
- Tremors and convulsions
- Muscle weakness
- Delirium
- Coma
Infection is seasonal and starts in spring with a peak incidence in August
(when mosquitoes are more common).
The encephalitis was most severe among the elderly and was often associated
with notable muscle weakness and even with flaccid paralysis.
When should a patient seek medical attention
When the signs and symptoms above appear in spring or summer and
especially if you live in an area that is known to have reported cases of
West Nile virus infection, you should seek medical attention.
Diagnosis
This should be confirmed by serum detection of antibodies (IgM) in the
serum of patients. PCR technique for the detection of viral DNA. Viral blood
cultures should be performed. A lumbar puncture and CSF (cerebrospinal fluid)
analysis of lymphocytic counts can help exclude septic meningitis due to
bacterial (not viral) infection.
Treatment
No specific viral therapy is available. Patients may need to be hospitalized
if they develop CNS disease. Treatment is usually limited to supportive
care. Some patients may require more aggressive supportive care in the intensive
care unit.
N.B.
- People should stay away from any dead animals, especially
birds.
- For more information about West Nile virus in a person's
community, contact should be made with local public health officials for
updated information.
| Article reviewed by: |
Dr. Tamer Fouad, M.D.
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| Edited
by: |
Jeffrey A. Gordon, M.D.
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Dr. Russell Musthafa
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Dr.Shariful Islam Sohel. MBBS,MESC.
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