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Introduction:
Aedes aegypti, a domestic, day-biting mosquito that prefers to feed on humans, is the most common Aedes species. Infections produce a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease.
Some 2500 million people,
two fifths of the world's population are now at risk from dengue.
Unprecedented population growth, mostly in developing tropical countries, has resulted in enormous urban sprawl, and unsanitary housing, water, sewage and waste systems. The result has been more
mosquitoes living closer to more people. Now, dengue is the most important mosquito-borne viral disease
affecting humans; its global distribution is comparable to that of malaria, and an estimated 2.5 billion people live in areas at risk for epidemic transmission.
In 2003 more than 220 people have been killed by two mosquito-borne viruses in India's
largest state U.P. alone in three months. Now in September
2006 the epidemic of Dengue is spreading rapidly all over India. WHO currently estimates there may be 50 million cases of dengue infection worldwide every year.
Dengue is a very fatal disease. The worst thing is that there is no specific
medicine to treat dengue. However, if proper steps are taken, then one can recover within two weeks.
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Causes of Dengue
Dengue is a mosquito-borne
infection caused by any one of four closely related viruses (DEN-1,
DEN-2, DEN-3 or DEN-4). Dengue viruses are transmitted to humans through the bites of
infected female
Aedes aegypti mosquitoes. Mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for 8-10 days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus, to susceptible individuals for the rest of its life. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of virus to humans has not yet been delineated. Humans are the main amplifying host of the virus, although studies have shown that in some parts of the world monkeys may become infected and perhaps serve as a source of virus for uninfected mosquitoes. The virus circulates in the blood of infected
humans for two to seven days, at approximately the same time as they have fever; Aedes mosquitoes may acquire the virus when they feed on an individual during this period.
As the major global demographic changes have occurred, the most important of which have been uncontrolled urbanization and concurrent population growth. These demographic changes have resulted in substandard housing and
inadequate water, sewer, and waste management systems, all of which increase
Aedes aegypti population densities and facilitate transmission of
Aedes aegypti borne disease. Changing life styles, in particular the spread of non-degradable plastic packaging, which makes ideal larval habitats for Aedes aegypti
mosquitoes. Another factor is the dramatic increase in automobiles and
discarded tires, which are equally useful to mosquito larva.
Increased commercial air travel is ideal for transporting dengue viruses (they travel inside their human victims) between population centers.
Lastly, effective mosquito control is virtually nonexistent in most dengue-endemic
in most of countries including India.
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Aedes aegypti
mosquitoes
Eggs of Aedes
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Sign and symptoms
The symptoms, following an incubation period of five to eight days, are
high fever, chills, severe headache, pain in the joints, nausea and
vomitting, eye pain sweating, and prostration. Symptoms subside in two to
seven days, but after a
remission lasting from a few hours to two days there is another rise in temperature, and a generalized
rash appears. Convalescence is sometimes prolonged, with weakness and low blood pressure.
Dengue hemorrhagic fever, a severe form of the disease, can cause hemorrhage, shock, and
encephalitis. It is a leading cause of death among children in
India.
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Diagnosis of Dengue
The diagnosis of dengue is usually made clinically. There exists a WHO definition of dengue haemorrhagic fever; all four criteria must be fulfilled:
Fever: Haemorrhagic tendency (positive tourniquet test, spontaneous bruising, bleeding from mucosa, gingiva, injection sites, etc.; vomiting blood, or bloody diarrhea)
Thrombocytopaenia: (Less than 100 platelets per mm³ or estimated as less than 3 platelets per high power field)
Evidence of plasma leakage (haematocrit more than 20% higher than expected, or drop in
haematocrit of 20% or more from baseline following IV fluid, pleural effusion,
ascites, hypoproteinaemia)
Dengue shock syndrome is defined as dengue haemorrhagic fever plus: Weak rapid pulse, and Narrow pulse pressure (less than 20 mm Hg)
or,
Hypotension for age; Cold, clammy skin and restlessness.
Serology and PCR (polymerase chain reaction) studies are available to confirm
the diagnosis of dengue if clinically indicated.
Treatment of Dengue
There is no specific medication for
treating a dengue infection or DHF. However, careful clinical management by experienced physicians and nurses frequently saves the lives of DHF patients. With appropriate intensive supportive therapy, mortality may be reduced to less than 1%. Maintenance of the circulating fluid volume is the central feature of DHF case management.
There is no specific medicine to treat dengue. However, if proper steps are taken, then one can recover within two weeks.
Those who are suffering from dengue should have proper bed rest, drink lots of
fluids and water and take
medicines to reduce fever.
Prevention and Control of Dengue
At present, the only method of controlling or preventing dengue and DHF is to combat the vector mosquitoes. In Asia and the Americas, Aedes aegypti breeds primarily in man-made containers like earthenware jars, metal drums and concrete cisterns used for domestic water storage, as well as discarded plastic food containers, used automobile tyres and other items that collect rainwater. In Africa it also breeds extensively in natural habitats such as tree holes and leaf axils. In recent years, Aedes albopictus, a secondary dengue vector in Asia, has become established in: the United States, several Latin American and Caribbean countries, in parts of Europe and in one African country. The rapid geographic spread of this species has been largely attributed to the international trade in used tyres. Vector control is implemented using environmental management and chemical methods. Proper solid waste disposal and improved water storage practices, including covering containers to prevent access by egg laying female mosquitoes are among methods that are encouraged through
community- based programmes.
The application of appropriate insecticides to larval habitats, particularly those which are considered useful by the householders, e.g. water storage vessels, prevent mosquito breeding for several weeks but must be re-applied periodically. Small, mosquito-eating fish and copepods (tiny crustaceans) have also been used with some success. During outbreaks, emergency control measures may also include the application of insecticides as space sprays to kill adult mosquitoes using portable or
truck- mounted machines or even aircraft. However, the killing effect is only transient, variable in its effectiveness because the aerosol droplets may not penetrate indoors to microhabitats where adult mosquitoes are sequestered, and the procedure is costly and operationally very demanding. Regular
monitoring of the vectors' susceptibility to the most widely used insecticides is necessary to ensure the appropriate choice of chemicals. Active monitoring and surveillance of the natural mosquito population should accompany control efforts in order to determine the impact of the
programme.
You can help to control Dengue:
1. Change water in your room cooler every day or at least after 3
days.
2. Add two spoonful of petrol or kerosene to stagnant water every
week to check mosquito.
3. Avoid the use of potted plants. If you have them at home, change
water every alternative days.
4 Be careful about storing pails
and watering cans.
5 You should keep the surrounding environment of your house and office clean.
Recent outbreak of Dengue in India
The spread of dengue is taking a serious turn in India. The dengue
fever is rapidly spreading in northern states of India mainly U.P.,
Punjab, Dehli, Rajasthan, M.P etc. Delhi is most affected by Dengu fever. Within last six weeks, thirteen people died in New
Delhi caused by dengu and a steady rising tally of cases are reported. New Delhi's health minister, Yoganand Shastri, told reporters the moves to stop the spread of dengue were aimed at keeping the outbreak from becoming an epidemic. But if "the outbreak is not contained by Tuesday,
the 3rd October 2006, we will declare it an epidemic," he told reporters.
The health minister of India called a meeting of four north Indian
states on 4th October 2006, as the disease is spreading fast. In
Rajasthan too nine deaths due to dengu fever are reported by the
Health Department of Rajasthan.
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History of Dengue :
Dengue haemorrhagic fever (DHF), a potentially lethal complication,
was first recognized in the 1950s during the dengue epidemics in the
Philippines and Thailand. The global prevalence of dengue has grown
dramatically in recent decades. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific. South-east Asia and the Western Pacific are most seriously affected. Before 1970 only nine countries had experienced DHF epidemics, a number that had increased more than four-fold by 1995.
In 2001 alone, there were more than 609 000 reported cases of dengue in the Americas, of which 15 000 cases were DHF. This is greater than double the number of dengue cases which were recorded in the same region in 1995.
In 2001, Brazil reported over 390 000 cases including more than 670 cases of
DHF. An estimated 500 000 cases of DHF require hospitalisation each year, of whom a very large proportion are children. At least 2.5% of cases
die.
Chikungunya
The same mosquito-borne virus that can cause an extremely painful, debilitating
illness is making a comeback in parts of India and the southwest Indian Ocean.
Chikungunya showing symptoms: include sudden fever followed by a crippling pain in the joints that can cause patients
to curl up. There is no vaccine or treatment other than painkillers. Chikungunya is rarely
fatal, but it has the potential to temporarily incapacitate. It's potentially
catastrophic, not only for health care, but also for workforce
implications.
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