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Virology


Dengue fever virus (DENV) is an RNA virus of the family Flaviviridae; genus Flavivirus. Other members of the same family include yellow fever virus, West Nile virus, St. Louis encephalitis virus, Japanese encephalitis virus, tick-borne encephalitis virus, Kyasanur forest disease virus, and Omsk hemorrhagic fever virus.[11] Most are transmitted by arthropods (mosquitoes or ticks), and are therefore also referred to as arboviruses (arthropod-borne viruses).[11]

The dengue virus genome (genetic material) contains about 11,000 nucleotide bases, which code for the three different types of protein molecules (C, prM and E) that form the virus particle and seven other types of protein molecules (NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5) that are only found in infected host cells and are required for replication of the virus.[12][13] There are four strains of the virus, which are called serotypes, and these are referred to as DENV-1, DENV-2, DENV-3 and DENV-4.[2] All four serotypes can cause the full spectrum of disease.[12] Infection with one serotype is believed to produce lifelong immunity to that serotype but only short term protection against the others.[2][7]

The severe complications on secondary infection occurs particularly if someone previously exposed to serotype DENV-1 then contracts serotype DENV-2 or serotype DENV-3, or if someone previously exposed to type DENV-3 then acquires DENV-2.

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DENGUE FEVER , HEALTH EDUCATION , INFECTION CONTROL (ICSP) , URDU

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Research

Research efforts to prevent and treat dengue include various means of vector control,[43] vaccine development, and antiviral drugs.[27] With regards to vector control, a number of novel methods have been used to reduce mosquito numbers with some success including the placement of the guppy (Poecilia reticulata) or copepods in standing water to eat the mosquito larvae.[43] There are ongoing programs working on a dengue vaccine to cover all four serotypes.[27] One of the concerns is that a vaccine could increase the risk of severe disease through antibody-dependent enhancement.[44] The ideal vaccine is safe, effective after one or two injections, covers all serotypes, does not contribute to ADE, is easily transported and stored, and is both affordable and cost-effective.[44] As of 2009, a number of vaccines were undergoing testing.[13][33][44] It is hoped that the first products will be commercially available by 2015.[27] Apart from attempts to control the spread of the Aedes mosq...
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Predisposition

Severe disease is more common in babies and young children, and in contrast to many other infections it is more common in children that are relatively well nourished.[5] Women are more at risk than men.[13] Dengue can be life-threatening in people with chronic diseases such as diabetes and asthma.[13] Polymorphisms (normal variations) in particular genes have been linked with an increased risk of severe dengue complications. Examples include the genes coding for the proteins known as TNFα, mannan-binding lectin,[1] CTLA4, TGFβ,[12] DC-SIGN, and particular forms of human leukocyte antigen.[13] A common genetic abnormality in Africans, known as glucose-6-phosphate dehydrogenase deficiency, appears to increase the risk.[22] Polymorphisms in the genes for the vitamin D receptor and FcγR seem to offer protection against severe disease in secondary dengue infection.
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