What is Dengue fever?
Dengue fever (pronounced Den-gay) is a viral infection caused by the
female mosquito (Aedes aegypti and Aedes albopictus). Dengue fever
occurs in tropical and sub-tropical regions and usually increases in
the hot and humid months. Dengue fever is not a new disease. It was
discovered several hundred years ago. In recent years, dengue fever
has become a major international public health concern.
Dengue fever nicknamed "breakbone fever" because dengue patients
usually express contorted movements due to intense joint and muscle
pain. Benjamin Rush from Philadelphia, US, first described "breakbone
fever" in 1780. Slaves who developed dengue fever in the West Indies
were said to have "dandy fever" because of their posture and gait.
Dengue fever lasts for approximately 7 days, despite its sudden and
acute onset. However, extra precautions should be taken after the
recovery period. These precautions will help prevent severe illness
from occurring in some people, such as dengue haemorrhagic fever (DHF)
or dengue shock syndrome (DSS). These illnesses are potentially
lethal and are today the leading cause of childhood mortality in
several Asian countries.
How is Dengue fever transmitted?
Dengue viruses are transmitted to humans (host) through the bites of
the female striped Aedes aegypti mosquito (vector). This variety of
mosquito breeds easily during the rainy seasons but can flourish in
peridomestic fresh water, e.g. water that is stored in plastic bags,
cans, flowerpots and old tires. The dengue virus is transmitted to
its host during probing and blood feeding. The mosquito may carry
the virus from one host to another host and the mosquito is most
active in the early morning and later afternoon. A mosquito bite can
cause the disease. Incubation period occurs when the viruses has
been transmitted to the human host. The period ranges from 3 to 15
days (usually lasting for 5-8 days) before the characteristics of
dengue appear. During incubation time, the dengue viruses multiply.
What are the characteristics of Dengue fever?
The Dengue virus travels to various glands in the body where it
multiples. It then travels to the bloodstream, affecting some
changes to these blood vessels. The virus may cause the blood
vessels to swell and leak. The spleen and lymph nodes may also
become swollen. Patches of liver tissue may die. Furthermore, a
process known as disseminated intravascular coagulation (DIC)
occurs. During this process, chemicals used to clot blood are used
up, and thus severe bleeding (hemorrhage) occurs internally as well
as the skin.
The signs and symptoms of Dengue fever are as follows:
- High fever (104 F, 40°C)
- Red eyes, pain in the eyes
- Enlarged lymph nodes
- Deep muscle and joint pains (during first hours of illness)
- Loss of appetite
- Nausea and vomiting
- Low blood pressure and heart rate
- Extreme fatigue
Basically, dengue commences with high fever and other signs as
listed above for 2 to 4 days. Then, the temperature drops rapidly
and intense sweating takes place. After about a day with normal
temperature and a feeling of well-being, the temperature rises
abruptly again. Rashes (small red bumps) show up on the arms, legs
and the entire body simultaneously along with fever. However, rashes
rarely occur on the face. The palms of the hands and soles of the
feet may be swollen and bright red. Although the patient may feel
exhausted for several weeks, most cases of dengue take approximately
one week to recover. Once a person recovers from dengue, he or she
will have antibodies in their bloodstream which will prevent them
from having a relapse for about a year.
There is no specific treatment to shorten the course of dengue
fever. Medications are given to alleviate the signs and symptoms.
Aspirin should not be given to patients. It will cause severe
bleeding. Hence, it is advisable to take paracetamol to relieve
muscle and joint aches, fever and headache. The patient may be
required to be sponged down with water at room temperature using a
wet, squeezed out towel for about 20 minutes at a time. This will
help to help lower the high temperature. Ice water should not be
used for this purpose. However, bed rest is essential to a speedy
recovery and the patient should consume plenty of water which will
help to alleviate the illness. Patients should be kept in a room
that has screens to prevent mosquitoes from entering or else under
mosquito netting until the second period of fever has subsided.
Hence, mosquitoes cannot bite them. If the patient is bitten then
the dengue virus may be transmitted to the mosquito and then to
What is Dengue Hemorrhagic Fever (DHF)?
Dengue hemorrhagic fever occurs when the dengue virus re-infects a
person who previously has experienced dengue fever. In this case,
the previous infection teaches the immune system to recognize the
virus, resulting in the immune system over reacting. DHF is also
known as dengue shock syndrome (DSS) and the symptoms in this case
are severe. It is a potential fatal immunological reaction and tends
to affect children under 15 years old.
The signs and symptoms of DHF are as follows:
- Abdominal pain
- Hemorrhage (severe bleeding)
- Circulatory collapse (shock)
- Nausea and vomiting
- Bleeding of the nose and gums
- Sore throat and cough
- Inflammation of the heart
- Blood in the stool
- High fever (40 -41 C)
The initial symptoms of DHF are high fever and severe headache.
Small purplish spots (petechiae) can be seen on the skin. This is
because blood is leaking out of the vessels. Large bruised areas
appear due to severe bleeding. Sometimes, patients may begin to
vomit a substance that appears as coffee grounds. This is actually a
sign of bleeding in the stomach. The severe hemorrhage results in a
decrease of blood in the body. The low blood flow will unable to
maintain adequate supply of blood to meet the metabolic requests of
the cells in the body. This state of low blood flow is the defined
as Dengue shock syndrome (DSS).
Patients with DHF must be closely monitored for the first few days
until their condition is stabilized. The patient's condition may
suddenly worsen after few days if the fever has not subsided. The
temperature will then suddenly drop and the patient shows signs of
circulatory failure. The patient may rapidly go into a critical
state of shock (DSS) and die within 12 to 24 hours. However, he or
she may recover quickly after appropriate volume replacement
therapy. Fluids are infused to patients to avoid dehydration.
Sometimes, blood transfusions may be necessary if severe bleeding
occurs. In addition, oxygen is given to cyanotic (bluish) patients.
Prevention and Control
At present, the only method of preventing and controlling dengue
fever is to eradicate the mosquito population. They are a number of
ways to combat the vector mosquitoes:
- Improved water storage practices. Cover all containers to prevent
egg laying female mosquitoes access to it.
- Implement proper solid waste disposal.
- Eliminate any sources that may collect water such as tins,
bottles, plastic food containers and old tires. Mosquitoes breed
easily in any source of standing water.
- Appropriate insecticides, such as larvicide's can be added to
water containers and man-made ponds. The insecticides can prevent
mosquitoes breeding for several weeks. However, they must be
re-applied as per directions.
- Always clean and check drains to ensure they are not blocked
especially during the rainy season.
- Breed small mosquito-eating fishes in an artificial pond to
eradicate the mosquito larvae.
In addition to the above, there are a number of factors to help
prevent the mosquito being attracted to human prey.
- Avoid wearing dark and tight clothing because mosquitoes are
attracted to dark colours. Wear loose, white and long clothes, which
cover the whole body. Mosquitoes find it difficult to bite through
loose clothes than tight fitting clothes.
- Environmental conditions. It is suggested to sleep under mosquito
netting or in a room which has mosquito screens on the windows.
Mosquitoes are unlikely to bite in an air-conditioned room and under
strong fans. Mosquito coils are also useful to help prevent
mosquitoes from entering the room.
- Apply mosquito repellants.
- Avoid reduce outdoor activities during morning and late afternoon
because Aedes mosquitoes are daytime feeders.
Modified GM Mosquitoes to fight dengue in Malaysia, October
Alert in Selangor,
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transmission, prevention, treatment in Malaysia
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consult a physician regarding health problems or medical conditions
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