2. WHAT IS DENGUE?
Dengue fever is a disease caused by a
family of viruses ( genus Flavivirus, family
Flaviviridae) that are transmitted by
mosquitoes ( Aedes aegypti).
It is an acute illness of sudden onset that
usually follows a benign course with
symptoms such as
headache, fever, exhaustion, severe
muscle and joint pain, swollen glands
(lymphadenopathy), and rash.
3. CAUSES OF DENGUE
There are four Dengue viruses (DENV) that cause
Dengue fever, all of which are spread by a species of
mosquito known as the Aedes aegypti mosquito, and
more rarely by the Aedes albopictus mosquito. Aedes
aegypti originated in Africa, but nowadays is found in
all the tropical areas around the world and prospers in
and close to areas of human population.
The virus is transmitted from an infected mosquito to
human. The process begins when a person who is
infected with the Dengue virus is bitten by a
mosquito, the virus is then passed on when someone
else is then bitten by the infected mosquito.
4. Signs and Symptoms
Mild Dengue Fever - symptoms can appear up to
seven days after the mosquito carrying the virus
bites, and usually disappear after a week. This form of the
disease hardly ever results in serious or fatal
complications. The symptoms of mild dengue fever are:
Aching muscles and joints
Body rashes that can disappear and then reappear
High fever
Intense headache
Pain behind the eyes
Vomiting and feeling nauseous
5.
6. Dengue hemorrhagic fever
(DHF) - symptoms during onset may be mild, but
gradually worsen after a number of days. DHF can
result in death if not treated in time. Mild dengue
fever symptoms may occur in DHF, as well as the
ones listed below:
•Bleeding from your mouth/gums
•Nosebleeds
•Clammy skin
•Considerably damaged lymph and blood vessels
•Internal bleeding, which can result in black vomit and feces (stools)
•Lower number of platelets in blood - these are the cells that help
clot your blood
•Sensitive stomach
7. Dengue shock syndrome
This is the worst form of dengue which can
also result in death, again mild dengue fever
symptoms may appear, but others likely to
appear are:
•Intense stomach pain
•Disorientation
•Sudden hypotension (fast drop in
blood pressure)
•Heavy bleeding
•Regular vomiting
•Blood vessels leaking fluid
•Death
8. MODE OF TRANSMISSION
Bites from infected females of
certain Aedes mosquito species. Ae. aegypti is the
major vector of dengue; Aedes albopictus can also
transmit DENV, but much less efficiently than Ae.
aegypti .
Ae. aegypti is a very domesticated, urban mosquito
found in the tropics and subtropics, and in Australia
is currently confined to Queensland; it usually breeds
in man-made containers and prefers
indoor, sheltered, dark resting sites. Humans are the
preferred source of blood meals for female Ae.
aegypti ; they are day-biting mosquitoes.
9. Ae. albopictus is a peri-domestic mosquito
found not only in the tropics and subtropics
but also some temperate regions. It is an
aggressive coloniser, but in Australia is
currently confined to the Torres Strait. It
breeds not only in artificial containers but
also in some naturally occurring sites such
as tree holes and coconut shells. Adults
prefer heavily-shaded outdoor resting sites;
the female takes blood from a wide range of
mammals. It is an aggressive day -biting
mosquito.
10. PERIOD OF
COMMUNICABILITY, RESISTANCE
AND SUSCEPTIBILITY
A human case is infective to mosquitoes from
shortly before, until the end of the period of
symptomatic viraemia; usually 4 - 5 days, but
can be longer.
For public health purposes, the duration of
viraemia is assumed to be from one day before
until 12 days after the onset of symptoms .
11. There is no direct person to person
transmission, but transfusion
related cases can occur.
Susceptibility to primary infection
appears universal. Recovery from
infection with one DENV serotype
provides lifelong immunity against
that serotype, but only short-term
protection against other serotypes.
12. Antibody dependent enhancement (ADE) is
an immunological phenomenon believed to
be responsible for the pathogenesis of
plasma leakage, a potentially severe
manifestation of dengue. In brief, following
infection with a particular DENV
serotype, the cross-protection against other
serotypes wanes after several months; at
some point the previously protected person
has, through ADE, an increased risk of
developing severe dengue following a
secondary infection (from another DENV
serotype).
13. It is hypothesized that ADE occurs in
the secondary infection when pre-
existing, but no longer
protective, antibodies enhance the
binding of the (secondary) virus to
macrophages and monocytes, leading to
increased virus replication in these
cells. This, in turn, leads to complement
activation and the release of various
cytokines that target vascular
endothelial cells, resulting in the leak
of plasma and protein.
14. Treatment for Dengue
There is no tested and approved
vaccine for the dengue flavivirus.
There is no specific medicine or
antibiotic to treat it.
For typical dengue, the treatment is
purely concerned with relief of the
symptoms (symptomatic). Close
monitoring of vital signs in the
critical period
15. Rest
and fluid intake for adequate
hydration is important.
Supplementation with intravenous
fluids may be necessary to prevent
dehydration and significant
concentration of the blood if the
patient is unable to maintain oral
intake.
Acetaminophen (Tylenol) and
codeine may be given for severe
headache and for the joint and
muscle pain (myalgia)
16. Platelettransfusion may be indicated if
the platelet level drops significantly
(below 20,000) or if there is significant
bleeding The presence of melena may
indicate internal gastrointestinal
bleeding requiring platelet and/or red
blood cell transfusion.
Aspirinand non-steroidal inflammatory
drugs should be avoided as these drugs
may worsen the bleeding tendency
17. METHODS OF CONTROL
•preventing mosquitoes from accessing egg-
laying habitats by environmental
management and modification;
•disposing of solid waste properly and
removing artificial man-made habitats;
•covering, emptying and cleaning of
domestic water storage containers on a
weekly basis;
•applying appropriate insecticides to water
storage outdoor containers;
18. • using of personal household protection such
as window screens, long-sleeved
clothes, insecticide treated materials, coils
and vaporizers;
• improving community participation and
mobilization for sustained vector control;
• applying insecticides as space spraying
during outbreaks as one of the emergency
vector control measures;
• active monitoring and surveillance of vectors
should be carried out to determine
effectiveness of control interventions.
19. PROGENY FOR PREVENTION
Clothing - your chances of being bitten are significantly
reduced if you expose as little skin as possible. When in an
area with mosquitoes, be sure to wear long trousers/pants, long
sleeved shirts, and socks. For further protection, tuck your
pant legs into your shoes or socks. Wear a hat.
Mosquito repellants - be sure to use one with at least 10%
concentration of DEET, you will need a higher concentration
the longer you need the protection, avoid using DEET on young
children.
Use mosquito traps and nets - studies have shown that the risk
of being bitten by mosquitoes is considerably reduced if you
use a mosquito net when you go to sleep
Smell - Avoid wearing heavily scented soaps and perfumes.
20. Windows- use structural barriers, such as
window screens or netting.
Camping - if you are camping, treat
clothes, shoes and camping gear with
permethrin. There are clothes which have
been treated with permethrin.
Certaintimes of day - try to avoid being
outside at dawn, dusk and early evening.
Stagnant water - the Aedes mosquito
prefers to breed in clean, stagnant water.
It is important to frequently check and
remove stagnant water in your
home/premises.
