3. What is dengue fever?
Dengue fever is a disease caused by a family of
viruses that are transmitted by mosquitoes.
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. The presence (the "dengue triad") of fever, rash
, and headache (and other pains) is particularly
characteristic of dengue. Other signs of dengue fever
include bleeding gums, severe pain behind the eyes,
and red palms and soles.
Dengue (pronounced DENG-gay) can affect anyone
but tends to be more severe in people with
compromised immune systems. Because it is caused
by one of four serotypes of virus, it is possible to get
dengue fever multiple times. However, an attack of
dengue produces immunity for a lifetime to that
particular serotype to which the patient was exposed.
4.
5. Dengue Fever
Dengue goes by other names, including "breakbone"
or "dandy fever."
Victims of dengue often have contortions due to the
intense joint and muscle pain, hence the name
breakbone fever.
Slaves in the West Indies who contracted dengue
were said to have dandy fever because of their
postures and gait.
Dengue hemorrhagic fever is a more severe form of
the viral illness.
Symptoms include headache, fever, rash, and
evidence of hemorrhage in the body.
Petechiae (small red or purple splotches or blisters
under the skin), bleeding in the nose or gums, black
stools, or easy bruising are all possible signs of
hemorrhage.
This form of dengue fever can be life-threatening
6. Dengue
Dengue is fast emerging pandemic-prone viral disease in many
parts of the world. Dengue flourishes in urban poor areas,
suburbs and the countryside but also affects more affluent
neighbourhoods in tropical and subtropical countries.
Dengue is a mosquito-borne viral infection causing a severe
flu-like illness and, sometimes causing a potentially lethal
complication called severe dengue.
The incidence of dengue has increased 30-fold over the last 50
years. Up to 50-100 million infections are now estimated to
occur annually in over 100 endemic countries, putting almost
half of the world’s population at risk.
Severe dengue (previously known as dengue haemorrhagic
fever) was first recognized in the 1950s during dengue
epidemics in the Philippines and Thailand.
Today it affects Asian and Latin American countries and has
become a leading cause of hospitalization and death among
children and adults in these regions.
Transmission
The full life cycle of dengue fever virus involves the role of
mosquito as a transmitter (or vector) and humans as the main
victim and source of infection.
7. The virus
The dengue virus (DEN)
comprises four distinct
serotypes (DEN-1, DEN-2, DEN-
3 and DEN-4) which belong to
the genus Flavivirus, family
Flaviviridae.
Distinct genotypes have been
identified within each serotype,
highlighting the extensive
genetic variability of the dengue
serotypes.
Among them, “Asian” genotypes
of DEN-2 and DEN-3 are
frequently associated with
severe disease accompanying
8. The Mosquito:
The Aedes aegypti mosquito is the main vector that transmits the viruses that cause
dengue. The viruses are passed on to humans through the bites of an infective female
Aedes mosquito, which mainly acquires the virus while feeding on the blood of an
infected person.
Within the mosquito, the virus infects the mosquito mid-gut and subsequently spreads
to the salivary glands over a period of 8-12 days. After this incubation period, the
virus can be transmitted to humans during subsequent probing or feeding. The
immature stages are found in water-filled habitats, mostly in artificial containers
closely associated with human dwellings and often indoors.
Flight range studies suggest that most female Ae. aegypti may spend their lifetime in
or around the houses where they emerge as adults and they usually fly an average of
400 metres. This means that people, rather than mosquitoes, rapidly move the virus
within and between communities and places.
Dengue infection rates are higher outdoors and during daytime, when these
mosquitoes (Stegomyia) bite most frequently. However, Ae. aegypti breed indoors and
are capable of biting anyone throughout the day. The indoor habitat is less susceptible
to climatic variations and increases the mosquitoes’ longevity.
Dengue outbreaks have also been attributed to Aedes albopictus, Aedes polynesiensis
and several species of the Aedes scutellaris complex. Each of these species has a
particular ecology, behaviour and geographical distribution. Ae. albopictus is primarily
a forest species that has become adapted to rural, suburban and urban human
environments. In recent decades Aedes albopictus has spread from Asia to Africa, the
Americas and Europe, notably aided by the international trade in used tyres in which
eggs are deposited when they contain rainwater. The eggs can withstand very dry
conditions (desiccation) and remain viable for many months in the absence of water
and the European strain of Aedes albopictus can undergo a period of reduced
development (diapause) during the winter months.
9. The human
Once infected, humans become the main carriers and
multipliers of the virus, serving as a source of the
virus for uninfected mosquitoes.
The virus circulates in the blood of an infected
person for 2-7 days, at approximately the same time
that the person develops a fever.
Patients who are already infected with the dengue
virus can transmit the infection via Aedes mosquitoes
after the first symptoms appear (during 4-5 days;
maximum 12).
In humans recovery from infection by one dengue
virus provides lifelong immunity against that
particular virus serotype.
However, this immunity confers only partial and
transient protection against subsequent infection by
the other three serotypes of the virus.
Evidence points to the fact that sequential infection
increases the risk of developing severe dengue.
The time interval between infections and the
10. Dengue Fever (DF) and Dengue
Haemorrhagic Fever (DHF) are the most
common mosquito-borne viral disease in
the world.
It can be fatal.
One distinct physical feature – black and
white stripes on its body and legs.
Bites during the day.
Lays its eggs in clean, stagnant water
Only the female Aedes mosquito feeds on
blood. This is because they need the
protein found in blood to produce eggs.
Male mosquitoes feed only on plant nectar.
On average, a female Aedes mosquito can
lay about 300 eggs during her life span of
14 to 21 days.
Mosquito-borne viral disease
12. Mode of Transmission
A healthy person gets the disease when he is
bitten by an infected mosquito. The virus
enters his blood from the mosquito’s saliva.
An infected person could transmit the virus to
mosquitoes if he is bitten by a mosquito
anytime from the onset to the subsidence of
the fever (a period of about 6 to 7 days). The
disease is then spread by mosquitoes.
Dengue fever is not spread by
Contact with infected persons.
14. Symptoms
A person infected by the dengue virus develops severe flu-like symptoms. The
disease, also called 'break-bone' fever affects infants, children and adults alike
and could be fatal. The clinical features of dengue fever vary according to the
age of the patient.
Individuals should suspect dengue when a high fever (40°C/ 104°F) is
accompanied by two of the following symptoms:
Severe headache
Pain behind the eyes
Nausea, Vomiting
Swollen glands
Muscle and joint pains
Rash
Symptoms usually last for 2-7 days, after an incubation period of 4-10 days
after the bite from an infected mosquito.
Severe dengue is a potentially deadly complication due to plasma leaking, fluid
accumulation, respiratory distress, severe bleeding, or organ impairment. The
warning signs to look out for occur 3-7 days after the first symptoms in
conjunction with a decrease in temperature (below 38°C/ 100°F) include:
Severe abdominal pain
Persistent vomiting
Rapid breathing
Bleeding gums
Blood in vomit
Fatigue, restlessness
The next 24-48 hours of the critical stage can be lethal; proper medical care is
needed to avoid complications and risk of death.
15. Treatment:
Patients infected with classical dengue
usually recovers in 1 to 2 weeks.
There is no specific treatment for
dengue fever.
Patients should seek medical advice,
rest and drink plenty of fluids.
Paracetamol can be taken to bring
down fever and reduce joint pains.
However, aspirin or ibuprofen should
not be taken since they can increase
the risk of bleeding.
For severe dengue, medical care by
physicians and nurses experienced
with the effects and progression of the
disease can frequently save lives.
Maintenance of the patient's
circulating fluid volume is the central
feature of such care.
16. Protect Yourself against Dengue
Fever
As yet, there is no effective vaccine against dengue
fever. Therefore, the best prevention is to avoid
being bitten by mosquitoes by paying attention to
the following:
Avoid staying in dark, outdoor places such as
brushwood, pavilions or the shade of a tree
during the hours when Aedes albopictus is
active.
17. Control the Spread of Dengue
Fever
Prevent the patient from being
bitten by mosquitoes.
18. Prevention of
Mosquito Bites
Avoid going out in the hours
when Aedes albopictus feed
or wear light-coloured,
long-sleeved clothing and
trousers.
19. Prevention of
Mosquito Bites
•Apply DEET-containing
mosquito-repellents
over exposed parts of
the body and clothes
every 4 to 6 hours.
•For DEET products
used by children, its
concentration should
be less than 10%.
20. Prevention of
Mosquito Bites
Your place of
accommodation should
have air-conditioners or
mosquito nets. Otherwise,
hang mosquito screens
around your bed, use
insecticides or coil
incenses to repel
mosquitoes.
22. Elimination of Mosquitoes
The most effective way
to eliminate mosquitoes
is to
keep the environment
clean and to remove
stagnant water so that
mosquitoes can’t
breed.
24. Elimination of Mosquitoes
• Dispose of domestic
wastes properly to
prevent the
accumulation of
stagnant water.
• Dispose of empty bottles,
cans and lunchboxes
properly, such as into a
covered bin.
25. Elimination of Mosquitoes
•Change water for vases
and aquatic plants at
least once a week,
leaving no water under
the pots or in the
bottom saucers.
•Scrub the container
surfaces thoroughly to
prevent mosquito eggs
29. Elimination of Mosquitoes
Remove stagnant
water immediately if
mosquitoes are found
to be breeding. Use
environmentally
friendly insecticides
such as lavicidal oil if
necessary.
30. Elimination of Mosquitoes
In cultivation ponds,
water tanks or large
containers, biological
controls such as
keeping fishes to eat
mosquito larvae
would be a good
option.
31. See Doctor Immediately
•Having been bitten by a
mosquito and displaying
symptoms of dengue fever
afterwards
•Falling ill, especially having a
fever within one month after
you
have returned from abroad
•If you suspect that you have
dengue fever, the most
important thing to do is to see
a doctor.
