Introduction
What is Dengue Fever?
Dengue fever is an infectious disease spread by mosquitoes and caused by dengue virus. Dengue virus is found mostly during and after the rainy reason in the tropical and sub- tropical areas of the world . It is also known as break bone fever, because it may cause severe joint and muscle pain.
Dengue is transmitted by Aedes mosquito. Its virus has four different sub - types (serotypes) . Infection with one serotype usually gives lifelong immunity against that type only. Since no vaccines are available , prevention is the best remedy.
This can be achieved by reducing the breeding sites of the mosquito and avoiding the contact of mosquito with human body.
History
1) Origin & Occurrence
The dengue viruses originated in monkeys and then these were transferred to human beings in Africa and South East Asia through mosquitoes . There is some evidence of an epidemic in 17th century . During the second world war, the co- incidental transport of Aedes mosquito in cargo is thought to be one of the major causes of spread of virus. In 1906 , Transmission by Aedes Mosquito was confirmed and by the year 1907 dengue was recognized as a major viral disease.
In Pakistan the First outbreak of dengue fever was recorded in karachi in 1994, which probably came from Thailand and Malaysia either through the trade of used tyres or through infected travellers. Then this disease moved towards Punjab, the most challenging and alarming situation was observed in lahore , during the year 2011, where it claimed many lives.
It should be mentioned here that in most of the cases dengue was not the only cause of reported deaths. The mortality was found to be associated with a number of other diseases of heart , Kidney and liver; the person was suffering from . These diseases had already weakened the immune system when dengue took over its job.
2) Geographical Distribution
Dengue is one of the most common viral disease transmitted by Aedes mosquito . The spread of dengue is due to expanding geographic geographic distribution of dengue virus and its vectors . The most important vector predominantly , is the urban species, Ae. aegypti . Dengue fever is most frequent in almost 100 tropical and sub tropical countries in the world . South East Asia, Africa and western pacific are the most seriously affected . Prior to 1970, only nine countries had experienced this epidemics .
WHO estimates that approximated 2.5 billion people are now at risk of dengue fever .An estimated 50-100 million cases of dengue fever occur each year. The incidence of dengue has increased 30 fold between 1960 and 2010 . This increase is believed to be related to the overall changes in climate and environment .
Various factors related to spread dengue
1) Global Warming
Rise in temperature due to global warming promotes viral reproduction and transmission through the mosquito . The spread of disease intensifies during rainy season. warm temperature and high humidity are the most favourite for mosquito . Dense population , high growth rate, urbanization , lack of sanitation and inefficient mosquito control further worsen the the scenario.
2) Population Growth
In the densely populated urban areas, chances of contact between man and mosquito increase. The controlling measures become inadequate as these do not match the rapidly growing population population.Nowadays the strategy of control has changed . More emphasis is given to limit the chances of contact between man and mosquito by the use of sprays, mosquito repellents, coils, and screen etc.
3) Urbanization
The increased population density (Number of people/sq.km) due to ill planned urbanization has disturbed the existing ecological balance resulting in the outbreak of disease in the form of an epidemic.
4) Poor Sanitation
Deterioration of public health infrastructure results in poor sanitary condition. Inadequate removal of the sewage and rain water, improper disposal of solid waste and unhygienic social conditions provide ideal breeding places for the mosquito.
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