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Transmission


Dengue virus is primarily transmitted by Aedes mosquitoes, particularly A. aegypti.[2] These mosquitoes usually live between the latitudes of 35° North and 35° South below an elevation of 1,000 metres (3,300 ft).[2] They bite primarily during the day.[14] Other Aedes species that transmit the disease include A. albopictus, A. polynesiensis and A. scutellaris.[2] Humans are the primary host of the virus,[2][11] but it also circulates in nonhuman primates.[15] An infection can be acquired via a single bite.[16] A female mosquito that takes a blood meal from a person infected with dengue fever becomes itself infected with the virus in the cells lining its gut. About 8–10 days later, the virus spreads to other tissues including the mosquito's salivary glands and is subsequently released into its saliva. The virus seems to have no detrimental effect on the mosquito, which remains infected for life. Aedes aegypti prefers to lay its eggs in artificial water containers, to live in close proximity to humans, and to feed off people rather than other vertebrates.[17]

Dengue can also be transmitted via infected blood products and through organ donation.[18][19] In countries such as Singapore, where dengue is endemic, the risk is estimated to be between 1.6 and 6 per 10,000 transfusions.[20] Vertical transmission (from mother to child) during pregnancy or at birth has been reported.[21] Other person-to-person modes of transmission have also been reported, but are very unusual.

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Laboratory tests

Dengue fever may be diagnosed by microbiological laboratory testing.[23] This can be done by virus isolation in cell cultures, nucleic acid detection by PCR, viral antigen detection or specific antibodies (serology).[13][25] Virus isolation and nucleic acid detection are more accurate than antigen detection, but these tests are not widely available due to their greater cost.[25] All tests may be negative in the early stages of the disease.[5][13] These laboratory tests are only of diagnostic value during the acute phase of the illness with the exception of serology. Tests for dengue virus-specific antibodies, types IgG and IgM, can be useful in confirming a diagnosis in the later stages of the infection. Both IgG and IgM are produced after 5–7 days. The highest levels (titres) of IgM are detected following a primary infection, but IgM is also produced in secondary and tertiary infections. The IgM becomes undetectable 30–90 days after a primary infection, but earlier following re-inf...
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Diagnosis

The diagnosis of dengue is typically made clinically, on the basis of reported symptoms and physical examination; this applies especially in endemic areas.[1] However, early disease can be difficult to differentiate from other viral infections.[5] A probable diagnosis is based on the findings of fever plus two of the following: nausea and vomiting, rash, generalized pains, low white blood cell count, positive tourniquet test, or any warning sign (see table) in someone who lives in an endemic area.[23] Warning signs typically occur before the onset of severe dengue.[8] The tourniquet test, which is particularly useful in settings where no laboratory investigations are readily available, involves the application of a blood pressure cuff for five minutes, followed by the counting of any petechial hemorrhages; a higher number makes a diagnosis of dengue more likely.[8] It can be difficult to distinguish dengue fever and chikungunya, a similar viral infection that shares many symptoms and ...
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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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