Dengue fever From Wikipedia, the free encyclopedia For other uses, see Dengue fever (disambiguation). Dengue fever, also known as breakbone fever, is a mosquito-borne tropical disease caused 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 inbleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs. Dengue is transmitted by several species of mosquito within the genus Aedes, principally A. aegypti. The virus has five different types;[1] 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, andintravenous fluids and blood transfusion for more severe cases. The number of cases of dengue fever has increased dramatically since the 1960s, with between 50 and 528 million people infected yearly.[2][3] Early descriptions of the condition date from 1779, and its viral cause and transmission were understood by 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 dengue vaccine, as well as medication targeted directly at the virus. Signs and symptoms Schematic depiction of the symptoms of dengue fever Typically, people infected with dengue virus are asymptomatic (80%) or have only mild symptoms such as an uncomplicated fever.[2][4][5] Others have more severe illness (5%), and in a small proportion it is life-threatening.[2][5] The incubation period (time between exposure and onset of symptoms) ranges from 3 to 14 days, but most often it is 4 to 7 days.[6] Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14 days after arriving home.[7] Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea)[8] and have a greater risk of severe complications,[7][9] though initial symptoms are generally mild but include high fever.[9] Clinical course Clinical course of dengue fever[10] 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, "breakbone fever", comes from the associated muscle and joint pains.[2][11] The course of infection is divided into three phases: febrile, critical, and recovery.[10] The febrile phase involves high fever, potentially over 40 °C (104 °F), and is associated with generalized pain and a headache; this usually lasts two to seven days.[10][11] Nausea and vomiting may also occur.[9] A rash occurs in 50–80% of those with symptoms[11][12] in the first or second day of symptoms as flushed skin, or later in the course of illness (days 4–7), as a measles-like rash.[12][13] A rash described as "islands of white in a sea of red" has also been observed.[14] Some petechiae (small red spots that do not disappear when the skin is pressed, which are caused by broken capillaries) can appear at this point,[10] as may some mild bleeding from the mucous membranes of the mouth and nose.[7][11] The fever itself is classically biphasic or saddleback in nature, breaking and then returning for one or two days.[13][14] The rash of dengue fever in the acute stage of the infection blanches when pressed In some people, the disease proceeds to a critical phase as fever resolves.[9] During this period, there is leakage of plasma from the blood vessels, typically lasting one to two days.[10] This may result in fluid accumulation in the chest and abdominal cavity as well as depletion of fluid from the circulation and decreased blood supply to vital organs.[10] There may also be organ dysfunction and severe bleeding, typically from the gastrointestinal tract.[7][10] Shock (dengue shock syndrome) and hemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue,[7] however those who have previously been infected with other serotypes of dengue virus ("secondary infection") are at an increased risk.[7][15] This critical phase, while rare, occurs relatively more commonly in children and young adults.[9] The rash that commonly forms during the recovery from dengue fever with its classic islands of white in a sea of red. The recovery phase occurs next, with resorption of the leaked fluid into the bloodstream.[10] This usually lasts two to three day
Signs and symptoms Schematic depiction of the symptoms of dengue fever Typically, people infected with dengue virus are asymptomatic (80%) or have only mild symptoms such as an uncomplicated fever.[2][4][5] Others have more severe illness (5%), and in a small proportion it is life-threatening.[2][5] The incubation period (time between exposure and onset of symptoms) ranges from 3 to 14 days, but most often it is 4 to 7 days.[6] Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14 days after arriving home.[7] Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea)[8] and have a greater risk of severe complications,[7][9] though initial symptoms are generally mild but include high fever.
Clinical course Clinical course of dengue fever[10] 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, "breakbone fever", comes from the associated muscle and joint pains.[2][11] The course of infection is divided into three phases: febrile, critical, and recovery.[10] The febrile phase involves high fever, potentially over 40 °C (104 °F), and is associated with generalized pain and a headache; this usually lasts two to seven days.[10][11] Nausea and vomiting may also occur.[9] A rash occurs in 50–80% of those with symptoms[11][12] in the first or second day of symptoms as flushed skin, or later in the course of illness (days 4–7), as a measles-like rash.[12][13] A rash described as "islands of white in a sea of red" has also been observed.[14] Some petechiae (small red spots that do not disappear when the skin is pressed, which are caused by broken capillaries) can appear at this point,[10] as may some mild bleeding from the mucous membranes of the mouth and nose.[7][11] The fever itself is classically biphasic or saddleback in nature, breaking and then returning for one or two days.[13][14] The rash of dengue fever in the acute stage of the infection blanches when pressed In some people, the disease proceeds to a critical phase as fever resolves.[9] During this period, there is leakage of plasma from the blood vessels, typically lasting one to two days.[10] This may result in fluid accumulation in the chest and abdominal cavity as well as depletion of fluid from the circulation and decreased blood supply to vital organs.[10] There may also be organ dysfunction and severe bleeding, typically from the gastrointestinal tract.[7][10] Shock (dengue shock syndrome) and hemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue,[7] however those who have previously been infected with other serotypes of dengue virus ("secondary infection") are at an increased risk.[7][15] This critical phase, while rare, occurs relatively more commonly in children and young adults.[9] The rash that commonly forms during the recovery from dengue fever with its classic islands of white in a sea of red. The recovery phase occurs next, with resorption of the leaked fluid into the bloodstream.[10] This usually lasts two to three days.[7] The improvement is often striking, and can be accompanied with severe itching and a slow heart rate.[7][10] Another rash may occur with either amaculopapular or a vasculitic appearance, which is followed by peeling of the skin.[9] During this stage, a fluid overload state may occur; if it affects the brain, it may cause a reduced level of consciousness or seizures.[7] A feeling of fatigue may last for weeks in adults.[9]
Associated problems Dengue can occasionally affect several other body systems,[10] either in isolation or along with the classic dengue symptoms.[8] A decreased level of consciousness occurs in 0.5–6% of severe cases, which is attributable either to inflammation of the brain by the virus or indirectly as a result of impairment of vital organs, for example, the liver.[8][14][16] Other neurological disorders have been reported in the context of dengue, such as transverse myelitis and Guillain-Barré syndrome.[8][16] Infection of the heart andacute liver failure are among the rarer complications.[7][10] Cause Virology Main article: Dengue virus A TEM micrograph showing dengue virus virions(the cluster of dark dots near the center) Dengue fever virus (DENV) is an RNA virus of the family Flaviviridae; genus Flavivirus. Other members of the same genus 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.[14] Most are transmitted by arthropods (mosquitoes or ticks), and are therefore also referred to as arboviruses (arthropod-borne viruses).[14] The dengue virus genome (genetic material) contains about 11,000 nucleotide bases, which code for the three different types of protein m