Dengue fever , also known as breakbone fever, is an infectious 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 in bleeding, 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 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 1779, 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.
Typically, people infected with dengue virus are asymptomatic (80%) or only have mild symptoms such as an uncomplicated fever.[1][2][3] Others have more severe illness (5%), and in a small proportion it is life-threatening.[1][3] The incubation period (time between exposure and onset of symptoms) ranges from 3–14 days, but most often it is 4–7 days.[4] Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14 days after arriving home.[5] Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea)[6] and have a greater risk of severe complications,[5][7] though initial symptoms are generally mild but include high fever.[7]
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.[8][9] Nausea and vomiting may also occur.[7] A rash occurs in 50–80% of those with symptoms[9][10] 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.[10][11] 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,[8] as may some mild bleeding from the mucous membranes of the mouth and nose.[5][9] The fever itself is classically biphasic in nature, breaking and then returning for one or two days, although there is wide variation in how often this pattern actually happens.[11][12]
In some people, the disease proceeds to a critical phase around the time fever resolves[7] and typically lasts one to two days.[8] During this phase there may be significant fluid accumulation in the chest and abdominal cavity due to increased capillary permeability and leakage. This leads to depletion of fluid from the circulation and decreased blood supply to vital organs.[8] During this phase, organ dysfunction and severe bleeding, typically from the gastrointestinal tract, may occur.[5][8] Shock (dengue shock syndrome) and hemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue,[5] however those who have previously been infected with other serotypes of dengue virus ("secondary infection") are at an increased risk.[5][13] This critical phase, while rare, occurs relatively more commonly in children and young adults.[7]
The recovery phase occurs next, with resorption of the leaked fluid into the bloodstream.[8] This usually lasts two to three days.[5] The improvement is often striking, and can be accompanied with severe itching and a slow heart rate.[5][8] Another rash may occur with either a maculopapular or a vasculitic appearance, which is followed by peeling of the skin.[7] During this stage, a fluid overload state may occur; if it affects the brain, it may cause a reduced level of consciousness or seizures.[5] A feeling of fatigue may last for weeks in adults.[7]
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 reinfection. IgM becomes undetectable 30–90 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 IgG reaches peak levels in the blood after 14–21 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.[9][14][36] The laboratory test for IgG and IgM antibodies can cross-react with other flaviviruses and may result in a false positive after recent infections or vaccinations with yellow fever virus or Japanese encephalitis.[7] 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.[36]
Dengue is transmitted by several species of mosquito within the genus Aedes, principally A. aegypti. 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 1779, 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.
Typically, people infected with dengue virus are asymptomatic (80%) or only have mild symptoms such as an uncomplicated fever.[1][2][3] Others have more severe illness (5%), and in a small proportion it is life-threatening.[1][3] The incubation period (time between exposure and onset of symptoms) ranges from 3–14 days, but most often it is 4–7 days.[4] Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14 days after arriving home.[5] Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea)[6] and have a greater risk of severe complications,[5][7] though initial symptoms are generally mild but include high fever.[7]
Most cases in the United States occur in people who
contracted the infection while traveling abroad. But the risk is
increasing for people living along the Texas-Mexico border and in other
parts of the southern United States. In 2009, an outbreak of dengue
fever was identified in Key West, Fla.
Dengue fever is transmitted by the bite of an Aedes
mosquito infected with a dengue virus. The mosquito becomes infected
when it bites a person with dengue virus in their blood. It can’t be spread directly from one person to another person.
Symptoms of Dengue Fever
Symptoms, which usually begin four to six days after infection and last for up to 10 days, may include
- Sudden, high fever
- Severe headaches
- Pain behind the eyes
- Severe joint and muscle pain
- Nausea
- Vomiting
- Skin rash, which appears three to four days after the onset of fever
- Mild bleeding (such a nose bleed, bleeding gums, or easy bruising)
Sometimes symptoms are mild and can be mistaken for those of the flu or another viral infection.
Younger children and people who have never had the infection before
tend to have milder cases than older children and adults. However,
serious problems can develop. These include dengue hemorrhagic fever, a
rare complication characterized by high fever, damage to lymph and blood
vessels, bleeding from the nose and gums, enlargement of the liver,
and failure of the circulatory system. The symptoms may progress to
massive bleeding, shock, and death. This is called dengue shock syndrome
(DSS).
People with weakened immune systems as well as those
with a second or subsequent dengue infection are believed to be at
greater risk for developing dengue hemorrhagic fever.
Diagnosing Dengue Fever
Doctors can diagnose dengue infection with a blood
test to check for the virus or antibodies to it. If you become sick
after traveling to a tropical area, let your doctor know. This will
allow your doctor to evaluate the possibility that your symptoms were
caused by a dengue infection.
Treatment for Dengue Fever
There is no specific medicine to treat dengue infection. If you think you may have dengue fever, you should use pain relievers with acetaminophen and avoid medicines with aspirin,
which could worsen bleeding. You should also rest, drink plenty of
fluids, and see your doctor. If you start to feel worse in the first 24
hours after your fever goes down, you should get to a hospital
immediately to be checked for 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, "breakbone fever", comes from the associated muscle and joint pains.[1][9] The course of infection is divided into three phases: febrile, critical, and recovery.[8]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.[8][9] Nausea and vomiting may also occur.[7] A rash occurs in 50–80% of those with symptoms[9][10] 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.[10][11] 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,[8] as may some mild bleeding from the mucous membranes of the mouth and nose.[5][9] The fever itself is classically biphasic in nature, breaking and then returning for one or two days, although there is wide variation in how often this pattern actually happens.[11][12]
In some people, the disease proceeds to a critical phase around the time fever resolves[7] and typically lasts one to two days.[8] During this phase there may be significant fluid accumulation in the chest and abdominal cavity due to increased capillary permeability and leakage. This leads to depletion of fluid from the circulation and decreased blood supply to vital organs.[8] During this phase, organ dysfunction and severe bleeding, typically from the gastrointestinal tract, may occur.[5][8] Shock (dengue shock syndrome) and hemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue,[5] however those who have previously been infected with other serotypes of dengue virus ("secondary infection") are at an increased risk.[5][13] This critical phase, while rare, occurs relatively more commonly in children and young adults.[7]
The recovery phase occurs next, with resorption of the leaked fluid into the bloodstream.[8] This usually lasts two to three days.[5] The improvement is often striking, and can be accompanied with severe itching and a slow heart rate.[5][8] Another rash may occur with either a maculopapular or a vasculitic appearance, which is followed by peeling of the skin.[7] During this stage, a fluid overload state may occur; if it affects the brain, it may cause a reduced level of consciousness or seizures.[5] A feeling of fatigue may last for weeks in adults.[7]
Laboratory tests
The diagnosis of dengue fever may be confirmed by microbiological laboratory testing.[28][34] This can be done by virus isolation in cell cultures, nucleic acid detection by PCR, viral antigen detection (such as for NS1) or specific antibodies (serology).[14][31] Virus isolation and nucleic acid detection are more accurate than antigen detection, but these tests are not widely available due to their greater cost.[31] Detection of NS1 during the febrile phase of a primary infection may be greater than 90% however is only 60–80% in subsequent infections.[7] All tests may be negative in the early stages of the disease.[5][14] PCR and viral antigen detection are more accurate in the first seven days.[7] In 2012 a PCR test was introduced that can run on equipment used to diagnose influenza; this is likely to improve access to PCR-based diagnosis.[35]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 reinfection. IgM becomes undetectable 30–90 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 IgG reaches peak levels in the blood after 14–21 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.[9][14][36] The laboratory test for IgG and IgM antibodies can cross-react with other flaviviruses and may result in a false positive after recent infections or vaccinations with yellow fever virus or Japanese encephalitis.[7] 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.[36]
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