dengue fever

Dengue Fever

Dr. Asra Hameed Dr. Asra Hameed Pharm.D (JUW) Pharm.D (JUW)

[email protected][email protected]

Dengue FeverDengue FeverDengueDengueTransmissionTransmissionThe virusThe virusThe mosquitoThe mosquitoThe humanThe humanSymptomsSymptomsTreatmentTreatmentPrevention and controlPrevention and control

Dengue Fever

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.

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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 and can progress to the most severe form of the illness, dengue shock syndrome.

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.

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 secondary dengue infections.

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.

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 particular viral sequence of infections may also be of importance.

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

1-2 days

Stagnant waterStagnant water

Pupae

4-5 days

Life cycle of the Aedes Mosquito

Larvae Eggs

2-3 days

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.

Transmission

Infected person

Healthy person

Infected mosquito

Incubation Period: 3 to 14 daysMost commonly 4 to 7 days

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.

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.

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.

Control the Spread of Dengue Fever

Prevent the patient from being bitten by mosquitoes.

Prevention of Mosquito Bites

Avoid going out in the hours when Aedes albopictus feed or wear light-coloured, long-sleeved clothing and trousers.


•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%.


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.


Install mosquito nets to doors and windows so that mosquitoes can’t get in.

Elimination of Mosquitoes

The most effective way to eliminate mosquitoes is tokeep the environment clean and to remove stagnant water so that mosquitoes can’t breed.


Cover water containers tightly so that mosquitoes can’t get in to lay eggs.


• 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.

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

sticking on them.


Remove or puncture any dumped tyres to prevent the accumulation of stagnant water.


Ditches should be free from blockage.


Fill up uneven ground surfaces to prevent the accumulation of stagnant water.


Remove stagnant water immediately if mosquitoes are found to be breeding. Use environmentally friendly insecticides such as lavicidal oil if necessary.


In cultivation ponds, water tanks or large containers, biological controls such as keeping fishes to eat mosquito larvae would be a good option.

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.

dengue fever

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