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Other seasonal
viral infections |
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Japanese Encephalitis |
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General Points |
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Japanese encephalitis
is caused by the Japanese encephalitis virus, an
arbovirus. |
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Encephalitis means
swelling of the brain. |
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The virus is spread by
the bite of an infected Culex mosquito which usually
bites at night. |
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Infection is
maintained in enzootic cycles between birds and
pigs: water birds (herons and egrets) are the main
reservoir for disseminating the virus whilst pigs
are important amplifier hosts. |
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It cannot spread
directly from one person to another. |
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Japanese Encephalitis in India |
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JE was clinically
diagnosed for the first time in India in 1955 at
Vellore, erstwhile North Arcot district of Tamil
Nadu. |
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Subsequently, the
outbreaks have occurred in 25 States / Union
Territories of India. |
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JE virus infection is
widespread and is particularly very high in Southern
States of India viz., Andra Pradesh (AP) Tamil Nadu
and some parts of Karnataka. |
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Sign and Symptoms |
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Japanese encephalitis can cause
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Mild infections with
fever and headache. |
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Severe infections with
encephalitis. |
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About 1 in 4 of such
cases results in death. |
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Symptoms of more
severe infection are headache, high fever, neck
stiffness, stupor, disorientation, abnormal
movements, occasional convulsions (especially in
infants), coma, and paralysis. |
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The infection may
start with fever, tiredness, headache, vomiting, and
sometimes confusion and agitation. |
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This may progress to
encephalitis (inflammation of the brain). This can
cause permanent brain damage and is fatal in some
cases. |
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Japanese is mainly a
problem in rural farming areas. |
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It occurs more
commonly in the rainy season (roughly May-September)
when the mosquitoes are most active. |
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Incubation period |
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Usually 5 to 15 days. |
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Mortality rate |
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Case-fatality rates range from 0.3% to upto 60%. |
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Diagnosis |
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Diagnosis is based on tests of blood or spinal fluid. |
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Treatment |
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There is no specific therapy. Intensive supportive therapy
is indicated. |
Prevention
As with any disease transmitted by mosquitoes, we can
prevent exposure to JE virus by: |
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Remaining in well
screened areas, |
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Wearing clothes that
cover most of the body, |
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Using an effective
insect repellent, such as those containing up to 30%
N,N-diethyl metatoluamide (DEET) on skin and
clothing. Use of permethrin on clothing will also
help prevent mosquito bites. |
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Japanese encephalitis
vaccine can prevent JE, however, JE vaccine is not
100% effective and is not a substitute for mosquito
precautions |
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Vaccination
High risk groups
Most travelers do not require the vaccine. Season, location
and duration of travel will determine who is at the highest
risk of disease. |
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People who live or
travel in certain rural parts of Asia should get the
vaccine. |
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Laboratory workers at
risk of exposure to JE virus should also be
vaccinated. |
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| Children 1-3 years of age get a
smaller dose than older children and adults. Children
younger than 1 year of age, pregnant, or a nursing mother
should not normally get the vaccine. JE vaccine can be given
at the same time as other vaccines. |
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