Hospital Authority
Prepared by: HA Central Committee on Infection Control
Issue Date: 28 June 2003
1.
Title: : Fact Sheet on Prevention and Management of
Japanese Encephalitis in Hospital
Page 1 of 4
Title
Fact sheet on Prevention and Management of Japanese Encephalitis in Hospital
2.
Purpose
To provide update information on the prevention and management of Japanese
Encephalitis in hospital.
3.
Epidemiology
Japanese Encephalitis (JE) virus is a member of the Flavivirus genus of the family
Flaviviridae.
Its genome is a positive sense single stranded RNA and has a single
serotype.
Infection by this arbovirus is endemic in tropical Asian countries and epidemic in
temperate regions of Asia. Affected countries include Russia, Japan, Korea, China, SE
Asian countries, India, Sri Lanka and North Queensland of Australia.
JE is very rare in Hong Kong.
From 1992 - till now, there have been a total of 5
sporadic cases reported in Hong Kong, including 1 local case in 1996, 1 imported case
in 1997, 1 imported case in 2001 and 2 imported cases in 2002.
Transmission
The main reservoirs are the pigs and birds which act as amplifying hosts. The virus is
transmitted between vertebrate hosts by rice-field-breeding mosquito. Humans are a
dead-end host, due to low viraemia.
The most important vector, Culex
tritaeniorhynchus is found in most parts of Asia. Other vectors include C. annulus, C.
vishnui, C. gelidus.
Most JE vectors are zoophilic, biting outdoors and active at
evening and night. Transmission usually is most prevalent in late summer and early fall
in temperate countries.
with peak at 3-5 years.
Children between 1 to 15 years of age are mainly affected
Elderly also tends to succumb to encephalitis. It is thought
that this is due to high level of immunity in adult population.
Prior dengue infection is associated with reduced mortality and better outcome due to
cross immunity.
4.
Incubation period 5-15 days
5.
Clinical features:
Most infection is asymptomatic. Mild cases present as febrile headache or aseptic
meningitis. The ratio of sub clinical to clinical infection is about 300:1. Severe disease
are marked by acute onset of fever, headache, meningeal signs, stupor, disorientation,
coma, tremors, convulsion, spastic or (rarely flaccid) paralysis. Some may present as
acute behavior change mimicking psychosis. Case fatality rate ranges from 10 to
35% .Neurological sequelae such as seizure disorders, motor and cranial nerve paresis,
cortical blindness and personality change occurs in 30 to 70% of survivors with highest
rate being reported in children.
JE in 1 and 2nd trimester of pregnancy may lead to fetal death and abortion.
Hospital Authority
Prepared by: HA Central Committee on Infection Control
Issue Date: 28 June 2003
Title: : Fact Sheet on Prevention and Management of
Japanese Encephalitis in Hospital
Page 2 of 4
Other complications are secondary bacterial infection especially pneumonia, urinary
tract infection and pressure ulcer during the lengthy recovery from coma and paralysis.
Important differential diagnosis in children in Asia
Bacterial meningitis, TB, malaria, herpes simplex encephalitis, enterovirus (particularly
enterovirus 71), West Nile virus, Nipah virus encephalitis, dengue with encephalopathy,
scrub typhus and rarely Guillain-Barre syndrome or acute psychosis.
6.
Laboratory diagnosis
JE virus can be detected by cell culture and recently by molecular technique but the
mainstay method still relies on serological diagnosis. Recent infection is confirmed by
demonstration of specific IgM in CSF and serum which are positive in most patient by 10
days after onset of illness (the commercial kit was recently redrawn from market and IgM
test is currently not available) or four fold changes of antibodies titre in acute and
convalescent serum by Hemagglutination inhibition test.
The haemagglutionation inhibition test is available in Government Virus Unit,
Department of Health.
7.
Reporting
Although JE is not a notifiable disease, it is prudent to monitor the trend in view of recent
outbreak in neighboring province. All suspected or confirmed cases viral encephalitis
should be reported to both DH Regional Offices and HAHO CCIC Secretariat (Fax no.
2881 5848) using Report Form as in appendix.
8.
Treatment:
No specific antiviral treatment is available. Supportive treatment should focus on
controlling seizure, ventilation support of respiratory failure, reducing cerebral edema,
keeping electrolytes and fluid balances and appropriate antibiotics for secondary
bacterial infection.
9.
Infection control measures
Isolation is not necessary in confirmed cases. Contact precaution is appropriate until
enterovirus meningoencephalitis is ruled out.
10. Prevention and control
1. Mosquito control
There is increasing problem of insecticide resistance in principal vector C.
tritaeniornynchus
2. Avoid mosquito bites: wear long sleeved cloth and pants or use insect repellents.
Avoid outside activities at dusk
3. Vaccines: killed and live attenuated vaccine from primary hamster kidney cells are
used in China. Formalin-inactivated mouse brain derived vaccine is used in children in
Japan, Korea, Thailand and Taiwan and Vietnam. Standard immunization schedule is 3
doses of 1ml given subcutaneously (0.5 ml for children) (0, 7, 28 day). Alternative
Hospital Authority
Prepared by: HA Central Committee on Infection Control
Issue Date: 28 June 2003
Title: : Fact Sheet on Prevention and Management of
Japanese Encephalitis in Hospital
Page 3 of 4
schedule is two doses given one to four weeks apart. Efficacy is more than 90%.
Periodic booster is needed every 3-4 years to maintain immunity. Local reaction and
fever occur in about 20% of vaccinees. Several cases of acute disseminated
encephalomyelitis temporarily associated with JE vaccination have been reported. (0.2
per 100,000 in one series) The principal vaccine-associated adverse effect of concern is
hypersensitivity consisting of generalized urticaria and angioedema 1 to 3 days after
vaccination. (about 0.6% of Western adult immunized for travel experienced allergic
reaction to components of vaccine). IgE antibodies to the gelatin stabilizer in the vaccine
have been suggested as the cause of allergic events. Individual with history of urticaria,
allergic rhinitis or other allergic reaction appear to be at higher risk.
Because of potentially serious adverse events, vaccination is not recommended
routinely outside endemic countries and is reserved for travelers visiting rural areas of
endemic countries for more than 30 days during transmission season. For further
information
visit
Hong
Kong
Travellers’
http://www.info.gov.hk/trhealth/e_HKTHS.htm.
Health
Service
website
at
Appendix
Report Form for Dengue Fever/Japanese Encephalitis*
* Please delete as appropriate
From : ___________________ Hospital
Date : ____________________
Reported by : _______________________________ (Name & Post)
_______________________________ (Contact telephone
This form should be send to the following:
(1) Department of Health Regional Offices
Fax no. : (HK : 2572 7582)
(Kln - 2375 8451)
(NTE: 2699 7691)
(NTW: 2439 9622)
(2) Secretariat, Central Committee on Infection Control, HAHO
(Fax no : 2881 5848)
(HA intranet mail : “Secretariat of Central Committee on Infection Control”)
number)
Name in
English (pls
affix patient
gum label)
Name in
Chinese
Sex/ Age
Home
address
Acknowledgement chop by CCIC Secretariat.
D:\533560550.doc
Place of
work/
school
attended
Date:
Confirmed/
Suspected
cases
Date of
Date of
A&E
admission
attendance
Onset date of
fever and/ or
symptom (pls
also specify the
symptom so
identified)
History of
travel
(place &
duration)
Remarks