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Other usespp-semi-indefInfobox disease| Name = Dengue fever| Image = Denguerash.JPG| Alt = Photograph of a person's back with the skin exhibiting the characteristic rash of dengue fever| Caption = The typical rash seen in dengue fever| ICD10 = ICD10|A|90||a|00| ICD9 = ICD9|061| DiseasesDB = 3564| MedlinePlus = 001374| eMedicineSubj = med| eMedicineTopic = 528| MeshName = Dengue| MeshNumber = C02.782.417.214 Dengue fever (IPA-en|'d??ge?|UK, IPA-en|'d??gi?|US), also known as breakbone fever , is an infectious tropical disease caused by the dengue virus . Symptoms include fever , headache , myalgia|muscle and arthralgia|joint pains , and a characteristic skin rash that is morbilliform|similar to measles . In a small proportion of cases the disease develops into the life-threatening dengue hemorrhagic fever , resulting in bleeding , thrombocytopenia|low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome , where Shock (circulatory)|dangerously low blood pressure occurs.
Dengue is transmitted by several species of mosquito within the genus Aedes , principally Aedes aegypti|A. aegypti . The virus has four different types; infection with one type usually gives lifelong immunity (medical)|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 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 therapy|intravenous fluids and blood transfusion for more severe cases. The Incidence (epidemiology)|incidence of dengue fever has increased dramatically since the 1960s, with around 50100& nbsp;million people infected yearly. Early descriptions of the condition date from 1779, and its viral cause and the transmission were elucidated in the early 20th century. Dengue has become a global problem since the World War II|Second World War and is endemic (epidemiology)|endemic in more than 110& nbsp;countries. Apart from eliminating the mosquitoes, work is ongoing on a vaccine, as well as medication targeted directly at the virus.
Signs and symptoms
Typically, people infected with dengue virus are asymptomatic (80%) or only have mild symptoms such as an uncomplicated fever.cite journal|author=Whitehorn J, Farrar J|title=Dengue|journal=Br. Med. Bull.|volume=95|pages=16173|year=2010|pmid=20616106|doi=10.1093/bmb/ldq019cite journal|author=Reiter P |title=Yellow fever and dengue: a threat to Europe? |journal=Euro Surveill |date=2010-03-11|volume=15|issue=10|pages=19509|pmid=20403310 | url= http://www.eurosurveillance.org/ViewArticle.aspx? ArticleId=19509 Others have more severe illness (5%), and in a small proportion it is life-threatening. The incubation period (time between exposure and onset of symptoms) ranges from 314 days, but most often it is 47 days. #refGubler2010|Gubler (2010) , p. 379. Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14& nbsp;days after arriving home. Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea),cite journal|author=Varatharaj A|title=Encephalitis in the clinical spectrum of dengue infection|journal=Neurol. India|volume=58|issue=4|pages=58591|year=2010|pmid=20739797|doi=10.4103/0028-3886.68655|url= http://www.neurologyindia.com/article.asp? issn=0028-3886;year=2010;volume=58;issue=4;spage=585;epage=591;aulast=Varatharaj and generally have less severe symptoms than adults,cite journal |author=Simmons CP, Farrar JJ, Nguyen vV, Wills B |title=Dengue |journal=N Engl J Med |volume=366 |issue=15 |pages=142332 |year=2012 |month=April |pmid=22494122 |doi=10.1056/NEJMra1110265 but are more susceptible to the severe complications.
Clinical course
The characteristic symptoms of dengue are sudden-onset fever, headache (typically located behind the eyes), muscle and joint pains, and a rash. The alternative name for dengue, "break-bone fever", comes from the associated muscle and joint pains.cite journal|author=Chen LH, Wilson ME|title=Dengue and chikungunya infections in travelers|journal=Curr. Opin. Infect. Dis.|volume=23|issue=5|pages=43844|year=2010|month=October|pmid=20581669 |doi=10.1097/QCO.0b013e32833c1d16 The course of infection is divided into three phases: febrile, critical, and recovery. #refWHO2009|WHO (2009) , pp. 2527.
The febrile phase involves high fever, often over convert|40|C|F, and is associated with generalized pain and a headache; this usually lasts two to seven days. At this stage, a rash occurs in 5080% of those with symptoms.cite book|author=Wolff K, Johnson RA (eds.)|title=Fitzpatrick's color atlas and synopsis of clinical dermatology|year=2009|publisher=McGraw-Hill Medical|location=New York|isbn=978-0-07-159975-7|chapter=Viral infections of skin and mucosa|edition=6th|pages=8102 It occurs in the first or second day of symptoms as erythema|flushed skin , or later in the course of illness (days 47), as a morbilliform|measles-like rash.cite book|author=Knoop KJ, Stack LB, Storrow A, Thurman RJ (eds.)|title=Atlas of emergency medicine|year=2010|publisher=McGraw-Hill Professional|location=New York|isbn=0-07-149618-1|chapter=Tropical medicine|edition=3rd | pages=6589 Some petechia e (small red spots that do not disappear when the skin is pressed, which are caused by broken capillary|capillaries ) can appear at this point, as may some mild bleeding from the mucous membrane s of the mouth and nose. The fever itself is classically fever#Types|biphasic in nature, breaking and then returning for one or two days, although there is wide variation in how often this pattern actually happens.
In some people, the disease proceeds to a critical phase, which follows the resolution of the high fever and typically lasts one to two days. During this phase there may be significant fluid accumulation in the thoracic cavity|chest and abdominal cavity due to increased Vascular permeability|capillary permeability and leakage. This leads to hypovolemia|depletion of fluid from the circulation and hypoperfusion|decreased blood supply to vital organs . During this phase, organ dysfunction and severe bleeding , typically from the gastrointestinal tract , may occur. Shock (circulatory)|Shock (dengue shock syndrome) and hemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue, however those who have previously been infected with other serotype s of dengue virus ("secondary infection") are at an increased risk.
The recovery phase occurs next, with resorption of the leaked fluid into the bloodstream. This usually lasts two to three days. The improvement is often striking, but there may be severe itch ing and a Bradycardia|slow heart rate . During this stage, a fluid overload state may occur; if it cerebral edema|affects the brain , it may cause a altered level of consciousness|reduced level of consciousness or Epileptic seizure|seizures .
Associated problems
Dengue can occasionally affect several other biological system|body systems , either in isolation or along with the classic dengue symptoms. A decreased level of consciousness occurs in 0.56% of severe cases, which is attributable either to encephalitis|infection of the brain by the virus or indirectly as a result of impairment of vital organs, for example, the hepatic encephalopathy|liver .cite journal|author=Gould EA, Solomon T|title=Pathogenic flaviviruses|journal= The Lancet |volume=371|issue=9611|pages=5009|year=2008|month=February|pmid=18262042|doi=10.1016/S0140-6736(08)60238-X
Other neurological disorders have been reported in the context of dengue, such as transverse myelitis and Guillain-Barrι syndrome . Myocarditis|Infection of the heart and acute liver failure are among the rarer complications.
Cause
Virology
Main|Dengue virus Dengue fever virus (DENV) is an RNA virus of the family Flaviviridae ; genus Flavivirus . Other members of the same genus include yellow fever|yellow fever virus , West Nile virus , St. Louis encephalitis|St. Louis encephalitis virus , Japanese encephalitis|Japanese encephalitis virus , tick-borne encephalitis virus , Kyasanur forest disease|Kyasanur forest disease virus , and Omsk hemorrhagic fever|Omsk hemorrhagic fever virus . Most are transmitted by arthropod s (mosquitoes or tick s), and are therefore also referred to as arbovirus es ( ar thropod- bo rne viruses).
The dengue virus genome (genetic material) contains about 11,000 nucleotide base s, which Genetic code|code for the three different types of protein molecules (C, prM and E) that form the Virion|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.cite journal|author=Rodenhuis-Zybert IA, Wilschut J, Smit JM|title=Dengue virus life cycle: viral and host factors modulating infectivity|journal=Cell. Mol. Life Sci.|volume=67|issue=16|pages=277386|year=2010|month=August|pmid=20372965|doi=10.1007/s00018-010-0357-zcite journal|author=Guzman MG, Halstead SB, Artsob H, et al. |title=Dengue: a continuing global threat|journal=Nat. Rev. Microbiol.|volume=8|issue=12 Suppl|pages=S7S16|year=2010|month=December|pmid=21079655|doi=10.1038/nrmicro2460|url= http://www.nature.com/nrmicro/journal/v8/n12_supp/full/nrmicro2460.html There are four strains of the virus, which are called serovar|serotype s, and these are referred to as DENV-1, DENV-2, DENV-3 and DENV-4. All four serotypes can cause the full spectrum of disease. Infection with one serotype is believed to produce lifelong immunity to that serotype but only short term protection against the others.
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.
Transmission
Dengue virus is primarily transmitted by Aedes mosquitoes, particularly Aedes aegypti|A. aegypti . #refWHO2009|WHO (2009) , pp.& nbsp;1416. These mosquitoes usually live between the latitude s of 35°& nbsp;North and 35°& nbsp;South below an elevation of convert|1000|m|ft. They bite primarily during the day. Other Aedes species that transmit the disease include Asian tiger mosquito|A. albopictus , Aedes polynesiensis|A. polynesiensis and Aedes scutellaris|A. scutellaris . Humans are the primary Host (biology)|host of the virus, but it also circulates in nonhuman primate s.cite web|title=Vector-borne viral infections|url= http://www.who.int/vaccine_research/diseases/vector/en/index1.html|publisher=World Health Organization|accessdate=17 January 2011 An infection can be acquired via a single bite.cite web|url= http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-5/dengue-fever-dengue-hemorrhagic-fever.aspx|title=Chapter 5 dengue fever (DF) and dengue hemorrhagic fever (DHF)|work=2010 Yellow Book|author=Center for Disease Control and Prevention|accessdate=2010-12-23 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 810 days later, the virus spreads to other tissues including the mosquito's salivary gland s 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. #refGubler2010|Gubler (2010) , pp.& nbsp;37778.
Dengue can also be transmitted via infected blood products and through organ donation .cite journal|author=Wilder-Smith A, Chen LH, Massad E, Wilson ME|title=Threat of dengue to blood safety in dengue-endemic countries|journal=Emerg. Infect. Dis.|volume=15|issue=1|pages=811|year=2009|month=January|pmid=19116042|pmc=2660677|doi=10.3201/eid1501.071097|url= http://www.cdc.gov/eid/content/15/1/8.htmcite journal|author=Stramer SL, Hollinger FB, Katz LM, et al. |title=Emerging infectious disease agents and their potential threat to transfusion safety|journal=Transfusion|volume=49 Suppl 2|pages=1S29S|year=2009|month=August|pmid=19686562|doi=10.1111/j.1537-2995.2009.02279.x In countries such as Singapore , where dengue is endemic, the risk is estimated to be between 1.6 and 6 per 10,000 blood transfusions|transfusions .cite journal|author=Teo D, Ng LC, Lam S|title=Is dengue a threat to the blood supply? |journal=Transfus Med|volume=19|issue=2|pages=6677|year=2009|month=April|pmid=19392949|pmc=2713854|doi=10.1111/j.1365-3148.2009.00916.x|url= http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3148.2009.00916.x/full Vertical transmission (from mother to child) during pregnancy or at birth has been reported.cite journal |author=Wiwanitkit V |title=Unusual mode of transmission of dengue |journal=Journal of Infection in Developing Countries |volume=4 |issue=1 |pages=514 |year=2010 |month=January |pmid=20130380 |doi= |url= http://www.jidc.org/index.php/journal/article/view/20130380 Other person-to-person modes of transmission have also been reported, but are very unusual.
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. Women are more at risk than men. Dengue can be life-threatening in people with chronic disease s such as diabetes mellitus|diabetes and asthma .
Polymorphism (biology)|Polymorphisms (normal variations) in particular gene s have been linked with an increased risk of severe dengue complications. Examples include the genes coding for the proteins known as Tumor necrosis factor-alpha|TNFa , mannan-binding lectin , CTLA4 , Transforming growth factor beta|TGFί , DC-SIGN , and particular allele|forms of human leukocyte antigen . A common genetic abnormality in Africans, known as glucose-6-phosphate dehydrogenase deficiency , appears to increase the risk.cite journal|author=Martina BE, Koraka P, Osterhaus AD|title=Dengue virus pathogenesis: an integrated view|journal=Clin. Microbiol. Rev.|volume=22|issue=4|pages=56481|year=2009|month=October|pmid=19822889|pmc=2772360|doi=10.1128/CMR.00035-09|url= http://cmr.asm.org/cgi/content/full/22/4/564 Polymorphisms in the genes for the Calcitriol receptor|vitamin D receptor and Fc receptor#Fc-gamma receptors|Fc?R seem to offer protection against severe disease in secondary dengue infection.
Mechanism
When a mosquito carrying dengue virus bites a person, the virus enters the skin together with the mosquito's saliva. It binds to and enters white blood cell s, and reproduces inside the cells while they move throughout the body. The white blood cells respond by producing a number of signaling proteins, such as interferon , which are responsible for many of the symptoms, such as the fever, the flu-like symptoms and the severe pains. In severe infection, the virus production inside the body is greatly increased, and many more organs (such as the liver and the bone marrow ) can be affected, and fluid from the bloodstream leaks through the wall of small blood vessels into body cavities. As a result, less blood circulates in the blood vessels, and the blood pressure becomes so low that it cannot supply sufficient blood to vital organs. Furthermore, dysfunction of the bone marrow leads to reduced numbers of platelets, which are necessary for effective blood clotting; this increases the risk of bleeding, the other major complication of dengue fever.
Viral replication
Once inside the skin, dengue virus binds to Langerhans cell s (a population of dendritic cell s in the skin that identifies pathogens). The virus Receptor-mediated endocytosis|enters the cells through binding between viral proteins and membrane protein s on the Langerhans cell, specifically the C-type lectin s called DC-SIGN, mannose receptor and CLEC5A . DC-SIGN, a non-specific receptor for foreign material on dendritic cells, seems to be the main point of entry. The dendritic cell moves to the nearest lymph node . Meanwhile, the virus genome is replicated in membrane-bound vesicles on the cell's endoplasmic reticulum , where the cell's protein synthesis apparatus produces new viral proteins, and the viral RNA is copied. Immature virus particles are transported to the Golgi apparatus , the part of the cell where some of the proteins receive necessary sugar chains ( glycoprotein s). The now mature new viruses bud on the surface of the infected cell and are released by exocytosis . They are then able to enter other white blood cells, such as monocyte s and macrophage s.
The initial reaction of infected cells is to produce interferon , a cytokine that raises a number of defenses against viral infection through the innate immune system by augmenting the production of a large group of proteins mediated by the JAK-STAT signaling pathway|JAK-STAT pathway . Some serotypes of dengue virus appear to have mechanisms to slow down this process. Interferon also activates the adaptive immune system , which leads to the generation of antibody|antibodies against the virus as well as T cell s that directly attack any cell infected with the virus. Various antibodies are generated; some bind closely to the viral proteins and target them for phagocytosis (ingestion by phagocyte|specialized cells and destruction), but some bind the virus less well and appear instead to deliver the virus into a part of the phagocytes where it is not destroyed but is able to replicate further.
Severe disease
Further|Antibody-dependent enhancementIt is not entirely clear why secondary infection with a different strain of dengue virus places people at risk of dengue hemorrhagic fever and dengue shock syndrome. The most widely accepted hypothesis is that of antibody-dependent enhancement (ADE). The exact mechanism behind ADE is unclear. It may be caused by poor binding of non-neutralizing antibodies and delivery into the wrong compartment of white blood cells that have ingested the virus for destruction. There is a suspicion that ADE is not the only mechanism underlying severe dengue-related complications, and various lines of research have implied a role for T cell s and soluble factors such as cytokine s and the complement system .
Severe disease is marked by two problems: dysfunction of endothelium (the cells that line blood vessels) and disordered coagulation|blood clotting . Endothelial dysfunction leads to the leakage of fluid from the blood vessels into the chest and abdominal cavities, while coagulation disorder is responsible for the bleeding complications. Higher viral load in the blood and involvement of other organs (such as the bone marrow and the liver ) are associated with more severe disease. Cells in the affected organs die, leading to the release of cytokines and activation of both coagulation and fibrinolysis (the opposing systems of blood clotting and clot degradation). These alterations together lead to both endothelial dysfunction and coagulation disorder.
Diagnosis
Warning signs div>
Abdominal pain
Ongoing vomiting
Liver enlargement
Mucosal bleeding
High hematocrit with low platelets
Lethargy
The diagnosis of dengue is typically made clinically, on the basis of reported symptoms and physical examination ; this applies especially in endemic areas. However, early disease can be difficult to differentiate from other viral infections . A probable diagnosis is based on the findings of fever plus two of the following: nausea and vomiting, rash, generalized pains, Leukopenia|low white blood cell count , positive tourniquet test , or any warning sign (see table) in someone who lives in an Endemic (epidemiology)|endemic area. Warning signs typically occur before the onset of severe dengue. The tourniquet test, which is particularly useful in settings where no laboratory investigations are readily available, involves the application of a Sphygmomanometer|blood pressure cuff for five minutes, followed by the counting of any petechial hemorrhages; a higher number makes a diagnosis of dengue more likely. It can be difficult to distinguish dengue fever and chikungunya , a similar viral infection that shares many symptoms and occurs in similar parts of the world to dengue. Often, investigations are performed to exclude other conditions that cause similar symptoms, such as malaria , leptospirosis , typhoid fever , and meningococcal disease .
The earliest change detectable on laboratory investigations is a low white blood cell count, which may then be followed by Thrombocytopenia|low platelets and metabolic acidosis . In severe disease, plasma leakage results in hemoconcentration (as indicated by a rising hematocrit ) and hypoalbuminemia . Pleural effusion s or ascites can be detected by physical examination when large, but the demonstration of fluid on medical ultrasonography|ultrasound may assist in the early identification of dengue shock syndrome. The use of ultrasound is limited by lack of availability in many settings.
Classification
The World Health Organization 's 2009 classification divides dengue fever into two groups: uncomplicated and severe. #refWHO2009|WHO (2009) , pp. 1011. This replaces the 1997 WHO classification, which needed to be simplified as it had been found to be too restrictive, though the older classification is still widely used. The 1997 classification divided dengue into undifferentiated fever, dengue fever, and dengue hemorrhagic fever.cite journal|author=Ranjit S, Kissoon N|title=Dengue hemorrhagic fever and shock syndromes|journal=Pediatr. Crit. Care Med.|year=2010|month=July|pmid=20639791|doi=10.1097/PCC.0b013e3181e911a7 |volume=12|pages=90100|issue=1 Dengue hemorrhagic fever was subdivided further into grades IIV. Grade I is the presence only of easy bruising or a positive tourniquet test in someone with fever, grade II is the presence of spontaneous bleeding into the skin and elsewhere, grade III is the clinical evidence of Shock (circulatory)|shock , and grade IV is shock so severe that blood pressure and pulse cannot be detected.cite book|author=WHO|url= http://www.who.int/csr/resources/publications/dengue/012-23.pdf|chapter=Chapter 2: clinical diagnosis|title=Dengue haemorrhagic fever: diagnosis, treatment, prevention and control|edition=2nd|location=Geneva|publisher=World Health Organization|pages=1223|year=1997|isbn=92-4-154500-3 Grades III and IV are referred to as "dengue shock syndrome".
Laboratory tests
Dengue fever may be diagnosed by microbiological laboratory testing. This can be done by virus isolation in cell culture s, Nucleic acid test|nucleic acid detection by polymerase chain reaction|PCR , viral antigen detection or specific antibodies (serology). #refWHO2009|WHO (2009) , pp.& nbsp;9095.Virus isolation and nucleic acid detection are more accurate than antigen detection, but these tests are not widely available due to their greater cost. All tests may be negative in the early stages of the disease.
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 57 days. The highest levels ( titre s) of IgM are detected following a primary infection, but IgM is also produced in secondary and tertiary infections. The IgM becomes undetectable 3090 days after a primary infection, but earlier following re-infections. IgG, by contrast, remains detectable for over 60 years and, in the absence of symptoms, is a useful indicator of past infection. After a primary infection the IgG reaches peak levels in the blood after 1421 days. In subsequent re-infections, levels peak earlier and the titres are usually higher. Both IgG and IgM provide protective immunity to the infecting serotype of the virus. In the laboratory test the IgG and the IgM antibodies can cross-react with other flaviviruses, such as yellow fever|yellow fever virus , which can make the interpretation of the serology difficult. The detection of IgG alone is not considered diagnostic unless blood samples are collected 14 days apart and a greater than fourfold increase in levels of specific IgG is detected. In a person with symptoms, the detection of IgM is considered diagnostic. #refGubler2010|Gubler (2010) , p.& nbsp;380.
Prevention
There are no approved vaccine s for the dengue virus. Prevention thus depends on control of and protection from the bites of the mosquito that transmits it. #refWHO2009|WHO (2009) , pp.& nbsp;5960. #refWHO2009|WHO (2009) , p.& nbsp;137. The World Health Organization recommends an Integrated Vector Control program consisting of five elements: (1)& nbsp;Advocacy, social mobilization and legislation to ensure that public health bodies and communities are strengthened, (2)& nbsp;collaboration between the health and other sectors (public and private), (3)& nbsp;an integrated approach to disease control to maximize use of resources, (4)& nbsp;evidence-based decision making to ensure any interventions are targeted appropriately and (5)& nbsp;capacity-building to ensure an adequate response to the local situation.
The primary method of controlling A. aegypti is by eliminating its habitat s. This is done by emptying containers of water or by adding insecticide s or biological control agent s to these areas, although spraying with organophosphate or pyrethroid insecticides is not thought to be effective. Reducing open collections of water through environmental modification is the preferred method of control, given the concerns of negative health effect from insecticides and greater logistical difficulties with control agents. People can prevent mosquito bites by wearing clothing that fully covers the skin, using mosquito net ting while resting, and/or the application of insect repellent ( DEET being the most effective).
Management
There are no specific treatments for dengue fever. Treatment depends on the symptoms, varying from oral rehydration therapy at home with close follow-up, to hospital admission with administration of Intravenous therapy|intravenous fluids and/or blood transfusion . #refWHO2009|WHO (2009) , pp.& nbsp;3237. A decision for hospital admission is typically based on the presence of the "warning signs" listed in the table above, especially in those with preexisting health conditions.
Intravenous hydration is usually only needed for one or two days. The rate of fluid administration is titrated to a Urination|urinary output of 0.51& nbsp;mL/kg/hr, stable vital signs and normalization of hematocrit . Invasive medical procedures such as nasogastric intubation , intramuscular injection s and arterial punctures are avoided, in view of the bleeding risk. Paracetamol (acetaminophen) is used for fever and discomfort while NSAIDs such as ibuprofen and aspirin are avoided as they might aggravate the risk of bleeding. Blood transfusion is initiated early in patients presenting with unstable vital signs in the face of a decreasing hematocrit , rather than waiting for the hemoglobin concentration to decrease to some predetermined "transfusion trigger" level. #refWHO2009|WHO (2009) , pp.& nbsp;4043. Packed red blood cells or whole blood are recommended, while platelet s and fresh frozen plasma are usually not.
During the recovery phase intravenous fluids are discontinued to prevent a state of Hypervolemia|fluid overload . If fluid overload occurs and vital signs are stable, stopping further fluid may be all that is needed. If a person is outside of the critical phase, a loop diuretic such as furosemide may be used to eliminate excess fluid from the circulation.
Epidemiology
See also|Dengue fever outbreaks Most people with dengue recover without any ongoing problems. The mortality is 15% without treatment, and less than 1% with adequate treatment; however severe disease carries a mortality of 26%. Dengue is Endemism|endemic in more than 110 countries. It infects 50 to 100& nbsp;million people worldwide a year, leading to half a million hospitalizations, and approximately 12,50025,000 deaths.cite web|author=WHO media centre|url= http://www.who.int/mediacentre/factsheets/fs117/en/|title=Dengue and dengue haemorrhagic fever|date=March 2009|publisher=World Health Organization|accessdate=2010-12-27
The most common viral disease transmitted by arthropod s, dengue has a disease burden estimated to be 1600 disability-adjusted life year s per million population, which is similar to other childhood and tropical diseases such as tuberculosis . As a tropical disease dengue is deemed only second in importance to malaria , though the World Health Organization counts dengue as one of sixteen neglected diseases|neglected tropical diseases .cite web|author=Neglected Tropical Diseases|url= http://www.who.int/neglected_diseases/diseases/en/|title=Diseases covered by NTD department|publisher=World Health Organization|accessdate=2010-12-27
The incidence of dengue increased 30& nbsp;fold between 1960 and 2010. #refWHO2009|WHO (2009) , p.& nbsp;3. This increase is believed to be due to a combination of urbanization, population growth, increased international travel, and global warming . The geographical distribution is around the equator with 70% of the total 2.5& nbsp;billion people living in endemic areas from Asia and the Pacific. In the United States, the rate of dengue infection among those who return from an endemic area with a fever is 2.98.0%, and it is the second most common infection after malaria to be diagnosed in this group.
Until 2003, dengue was classified as a potential bioterrorism agent, but subsequent reports removed this classification as it was deemed too difficult to transfer and only caused hemorrhagic fever in a relatively small proportion of people.
Like most arboviruses, dengue virus is maintained in nature in cycles that involve preferred blood-sucking vectors and vertebrate hosts. The viruses are maintained in the forests of Southeast Asia and Africa by transmission from female Aedes mosquitoesof species other than A. aegypti to her offspring and to lower primates. In rural settings the virus is transmitted to humans by A. aegypti and other species of Aedes such as Aedes albopictus|A. albopictus . In towns and cities, the virus is primarily transmitted to humans by A. aegypti , which is highly domesticated. In all settings the infected lower primates or humans greatly increase the number of circulating dengue viruses. This is called amplification. #refGubler2010|Gubler (2010) , pp.& nbsp;376. The urban cycle is the most important to infections of humans and dengue infections are primarily confined to towns and cities. #refGubler2010|Gubler (2010) , pp.& nbsp;377. In recent decades, the expansion of villages, towns and cities in endemic areas, and the increased mobility of humans has increased the number of epidemics and circulating viruses. Dengue fever, which was once confined to Southeast Asia, has now spread to Southern China, countries in the Pacific Ocean and America, and might pose a threat to Europe.
History
The first record of a case of probable dengue fever is in a Chinese medical encyclopedia from the Jin Dynasty (265420)|Jin Dynasty (265420& nbsp;AD) which referred to a "water poison" associated with flying insects.cite journal|author=Gubler DJ|title=Dengue and dengue hemorrhagic fever|journal=Clin. Microbiol. Rev.|volume=11|issue=3|pages=48096|year=1998|month=July|pmid=9665979|pmc=88892|url= http://cmr.asm.org/cgi/content/full/11/3/480 There have been descriptions of epidemics in the 17th century, but the most plausible early reports of dengue epidemics are from 1779 and 1780, when an epidemic swept Asia, Africa and North America. From that time until 1940, epidemics were infrequent.
In 1906, transmission by the Aedes mosquitoes was confirmed, and in 1907 dengue was the second disease (after yellow fever ) that was shown to be caused by a virus.cite journal|author=Henchal EA, Putnak JR|title=The dengue viruses|journal=Clin. Microbiol. Rev.|volume=3|issue=4|pages=37696|year=1990|month=October|pmid=2224837|pmc=358169|url= http://cmr.asm.org/cgi/reprint/3/4/376|doi=10.1128/CMR.3.4.376 Further investigations by John Burton Cleland and Joseph Franklin Siler completed the basic understanding of dengue transmission.
The marked spread of dengue during and after the World War II|Second World War has been attributed to ecologic disruption. The same trends also led to the spread of different serotypes of the disease to new areas, and to the emergence of dengue hemorrhagic fever. This severe form of the disease was first reported in the Philippines in 1953; by the 1970s, it had become a major cause of child mortality and had emerged in the Pacific and the Americas. Dengue hemorrhagic fever and dengue shock syndrome were first noted in Central and South America in 1981, as DENV-2 was contracted by people who had previously been infected with DENV-1 several years earlier.
Etymology
The origins of the word "dengue" are not clear, but one theory is that it is derived from the Swahili language|Swahili phrase Ka-dinga pepo , which describes the disease as being caused by an evil spirit . The Swahili word dinga may possibly have its origin in the Spanish word dengue , meaning fastidious or careful, which would describe the gait of a person suffering the bone pain of dengue fever.cite web|url= http://www.etymonline.com/index.php? term=dengue|title=Etymology: dengue|year=2001|work=Online Etymology Dictionary|author=Harper D|accessdate=2008-10-05 However, it is possible that the use of the Spanish word derived from the similar-sounding Swahili.cite journal|author=Anonymous|title=Etymologia: dengue|journal=Emerg. Infec. Dis.|year=2006|volume=12|page=893|url= http://www.cdc.gov/ncidod/eid/vol12no06/pdfs/etymology.pdf|issue=6 Slaves in the West Indies having contracted dengue were said to have the posture and gait of a dandy , and the disease was known as "dandy fever".cite web|author=Anonymous|url= http://www.medterms.com/script/main/art.asp? articlekey=6620|title=Definition of Dandy fever|work=MedicineNet.com|date=1998-06-15|accessdate=2010-12-25cite book|author=Halstead SB|title=Dengue (Tropical Medicine: Science and Practice)|publisher=Imperial College Press|location=River Edge, N.J|year=2008|pages=110|isbn=1-84816-228-6|url= http://books.google.com/books? id=6zLd9mFwxwsC& pg=PA1
The term "break-bone fever" was first applied by physician and Founding Fathers of the United States|Founding Father Benjamin Rush , in a 1789 report of the 1780 epidemic in Philadelphia . In the report he uses primarily the more formal term "bilious remitting fever".cite book|author=Rush AB|year=1789|chapter=An account of the bilious remitting fever, as it appeared in Philadelphia in the summer and autumn of the year 1780|title=Medical enquiries and observations|pages=104117|publisher=Prichard and Hall|location=Philadelphia The term dengue fever came into general use only after 1828. Other historical terms include "breakheart fever" and "la dengue". Terms for severe disease include "infectious thrombocytopenic purpura" and "Philippine", "Thai", or "Singapore hemorrhagic fever".
Research
Research efforts to prevent and treat dengue include various means of vector control, #refWHO2009|WHO (2009) , p.& nbsp;71. vaccine development, and antiviral drug s. #refWHO2009|WHO (2009) p. 137146.
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.
There are ongoing programs working on a dengue vaccine to cover all four serotypes. One of the concerns is that a vaccine could increase the risk of severe disease through antibody-dependent enhancement.cite journal|author=Webster DP, Farrar J, Rowland-Jones S|title=Progress towards a dengue vaccine|journal=Lancet Infect Dis|volume=9|issue=11|pages=67887|year=2009|month=November|pmid=19850226|doi=10.1016/S1473-3099(09)70254-3 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. As of 2009, a number of vaccines were undergoing testing.cite book|author=Barrett AD, Stanberry LR|title=Vaccines for biodefense and emerging and neglected diseases|publisher=Academic|location=San Diego|year=2009|pages=287323|isbn=0-12-369408-6|url= http://books.google.co.uk/books? id=6Nu058ZNa1MC& pg=PA289 It is hoped that the first products will be commercially available by 2015.
Apart from attempts to control the spread of the Aedes mosquito and work to develop a vaccine against dengue, there are ongoing efforts to develop antiviral drug s that would be used to treat attacks of dengue fever and prevent severe complications.cite journal|author=Sampath A, Padmanabhan R|title=Molecular targets for flavivirus drug discovery|journal=Antiviral Res.|volume=81|issue=1|pages=615|year=2009|month=January|pmid=18796313|pmc=2647018|doi=10.1016/j.antiviral.2008.08.004cite journal|author=Noble CG, Chen YL, Dong H, et al. |title=Strategies for development of Dengue virus inhibitors|journal=Antiviral Res.|volume=85|issue=3|pages=45062|year=2010|month=March|pmid=20060421|doi=10.1016/j.antiviral.2009.12.011 Discovery of the structure of the viral proteins may aid the development of effective drugs. There are several plausible targets. The first approach is inhibition of the viral RNA-dependent RNA polymerase (coded by NS5), which copies the viral genetic material, with nucleoside analog s. Secondly, it may be possible to develop specific Protease inhibitor (pharmacology)|inhibitors of the viral protease (coded by NS3), which protein splicing|splices viral proteins.cite journal|author=Tomlinson SM, Malmstrom RD, Watowich SJ|title=New approaches to structure-based discovery of dengue protease inhibitors|journal=Infectious Disorders Drug Targets|volume=9|issue=3|pages=32743|year=2009|month=June|pmid=19519486 Finally, it may be possible to develop entry inhibitor s, which stop the virus entering cells, or inhibitors of the 5' cap|5' cap ping process, which is required for viral replication.
Notes
Reflist|30em
References
Refbegin
cite book|author=Gubler DJ|editor=Mahy BWJ, Van Regenmortel MHV|title=Desk Encyclopedia of Human and Medical Virology|chapter=Dengue viruses|publisher=Academic Press|location=Boston|year=2010|isbn=0-12-375147-0|url= http://books.google.com/books? id=nsh48WKIbhQC& pg=PA372 | pages=37282
cite book|author=WHO|url= http://whqlibdoc.who.int/publications/2009/9789241547871_eng.pdf|title=Dengue Guidelines for Diagnosis, Treatment, Prevention and Control|location=Geneva|publisher=World Health Organization|year=2009|isbn=92-4-154787-1
cite web|url= http://www.who.int/topics/dengue/en/|title=Dengue|publisher= World Health Organization|WHO |accessdate=2011-06-27
cite web|url= http://www.cdc.gov/dengue/|title=Dengue|publisher=U.S. Centers for Disease Control and Prevention |accessdate=2011-06-27
cite web|url= http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/DengueFever/|title=Dengue fever|publisher=UK Health Protection Agency |accessdate=2011-06-27
cite web|url= http://www.healthmap.org/dengue/|title=DengueMap|publisher=U.S. Centers for Disease Control and Prevention/ HealthMap |accessdate=2011-06-27
Zoonotic viral diseases Use dmy dates|date=February 2011 featured article DEFAULTSORT:Dengue Fever Category:Arthropod-borne viral fevers and viral haemorrhagic fevers Category:Tropical diseases Category:Hemorrhagic fevers Category:Insect-borne diseases Category:Health disasters in India Category:Neglected diseases Category:Virus-related cutaneous conditions