BEJAR, MALAIKA GABALDON, VANESSA

CELINEPD2F

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.

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. 

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Signs and SymptomsMild 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

7Dengue 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 l isted 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

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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

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MODE OF TRANSMISSIONBites 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.

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.

7PERIOD 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.

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.

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).

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.

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

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)

Platelet transfusion 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.

Aspirin and non-steroidal inflammatory drugs should be avoided as these drugs may worsen the bleeding tendency

7METHODS 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;

• 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.

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.

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.

Certain times 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. 

The End