The dengue virus (DENV) in one of four serotypes and the cause of dengue fever. All four serotypes can cause the full spectrum of disease. It Is a mosquito-borne, single positive-stranded RNA virus of the family Flavlvlrldae; genus Flavlvlrus. Its genome Is about 11000 bases that codes for three structural proteins, capsid protein C, membrane protein M, envelope protein E; seven nonstructural proteins, NSI, NS2a, NS2b, NS3, NS4a, NS4b, NS5; and short non-codlng regions on both the 5′ and 3′ ends.

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Based on the analysis of the envelope protein there are at least four genotypes (1 to 4) – The American African genotype has been estimated to have evolved between 1907 to 1949. This period includes World War I and II which were associated with considerable movement of populations and environmental disturbance. factors known to promote the evolution of new vector borne viral species. until a few hundred years ago dengue virus was transmitted in sylvatic cycles in Africa and Asia between mosquitoes of the genus Aedes and non-human primates with rare emergences into human populations.

The global spread of dengue virus, however, has followed its emergence from sylvatic cycles and the primary life cycle now exclusively involves transmission between humans and Aedes mosquitoes. The reason that some people suffer from more severe forms of dengue, such as dengue hemorrhagic fever, is multifactorial. Among the possible causes are cross- serotypic immune response, through a mechanism known as antibody-dependent enhancement, which happens when a person who has been previously Infected with dengue gets infected for the second, third or fourth time.

The previous antibodies to he old strain of dengue virus now Interfere with the Immune response to the current strain, leading paradoxically to more virus entry and uptake. There currently Is no human vaccine available. Developing a vaccine against the disease Is challenging. With four different serotypes of the dengue virus that can cause the disease, the vaccine must Immunize against all four types to be effective. Vaccination against only one serotype could possibly lead to severe dengue hemorrhagic shock (DHS) when Infected with another serotype due to antibody-dependent enhancement.

Page 2 Dengue notes Essay

It Is estimated that a vaccine will be available In 2014. by the dengue virus. Symptoms include fever, headache, muscle and Joint pains, and a characteristic skin rash that is similar to measles. In a small proportion of cases the disease develops into the life-threatening dengue hemorrhagic fever,resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.

The virus has four different types; infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications. As there is no commercially available vaccine, prevention is sought by reducing the habitat and the number of mosquitoes and limiting exposure to bites. Treatment of acute dengue is supportive, using either oral or intravenous rehydration for mild or moderate disease, and intravenous fluids and blood transfusion for more severe cases.

The incidence of dengue fever has increased dramatically since the 1960s, with around 50-100 million people infected yearly. Early descriptions of the condition date from 779, and its viral cause and the transmission were elucidated in the early 20th century. Dengue has become a global problem since the Second World War and is endemic in more than 110 countries. Apart from eliminating the mosquitoes, work is ongoing on a vaccine, as well as medication targeted directly at the virus.

With more than one-third of the world’s population living in areas at risk for transmission, dengue infection is a leading cause of illness and death in the tropics and subtropics. As many as 100 million people are infected yearly. Dengue is caused by any one of four related viruses transmitted by mosquitoes. There are not yet any vaccines to prevent infection with dengue virus (DENV) and the most effective protective measures are those that avoid mosquito bites.

Dengue has emerged as a worldwide problem only since the 1950s. Although dengue rarely occurs in the continental United States, it is endemic in Puerto Rico, and in many popular tourist destinations in Latin America and Southeast Asia; periodic outbreaks occur in Samoa and Guam. Dengue infections are caused by one of four virus serotypes of the genus Flavivirus and are transmitted via Aedes aegypti and Aedes albopictus mosquitoes (Gubler 989; Sulaiman et al. 2002; World Health Organization 2004).

A secondary infection with a differing serotype can lead to dengue hemorrhagic fever (DHF) or dengue shock syndrome. The case fatality rate for dengue fever is usually less than 1%; however, in extreme circumstances the rate for DHF can exceed 20% (World Health Organization 2002). Aedes aegypti prefer sheltered domestic environ- ments and commonly breed in artificial containers with fresh water such as flower vases,

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