[15] Already endemic in more than one hundred countries, dengue is spreading from tropical and subtropical regions to the Iberian Peninsula and the southern states of the US, partly attributed to climate change.

[20] The characteristic symptoms of mild dengue are sudden-onset fever, headache (typically located behind the eyes), muscle and joint pains, nausea, vomiting, swollen glands and a rash.

[38] For 2 to 10 days after becoming newly infected, a person's bloodstream will contain a high level of virus particles (the viremic period).

A female mosquito that takes a blood meal from the infected host then propagates the virus in the cells lining its gut.

[42] This is more probable in areas where the disease is endemic, especially where there is high population density, poor sanitation, and standing water where mosquitoes can breed.

[42] It can be mitigated by taking steps to avoid bites such as by wearing clothing that fully covers the skin, using mosquito netting while resting, and/or the application of insect repellent (DEET being the most effective).

[43] Other risk factors for severe disease include female sex, and high body mass index,[21][30] Infection with one serotype is thought to produce lifelong immunity to that type, but only short-term protection against the other three.

[22] Subsequent re-infection with a different serotype increases the risk of severe complications due to phenomenon known as antibody-dependent enhancement (ADE).

[45] It appears that ADE occurs when the antibodies generated during an immune response recognize and bind to a pathogen, but they fail to neutralize it.

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.

Fluid from the bloodstream leaks through the wall of small blood vessels into body cavities due to increased capillary permeability.

The spread of the virus to 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.

[1] This is more probable in areas where the disease is endemic, especially where there is high population density, poor sanitation, and standing water where mosquitoes can breed.

[50] Protection of the home can be achieved with door and window screens, by using air conditioning, and by regularly emptying and cleaning all receptacles both indoors and outdoors which may accumulate water (such as buckets, planters, pools or trashcans).

[55] Due to safety concerns about antibody-dependent enhancement (ADE), it should only be given to individuals who have previously been infected with dengue, in order to protect them from reinfection.

[53] The World Health Organization's International Classification of Diseases divides dengue fever into two classes: uncomplicated and severe.

[60] Mild cases of dengue fever can easily be confused with several common diseases including Influenza, measles, chikungunya, and zika.

[61][62] Dengue, chikungunya and zika share the same mode of transmission (Aedes mosquitoes) and are often endemic in the same regions, so that it is possible to be infected simultaneously by more than one disease.

[21] Warning symptoms of severe dengue include abdominal pain, persistent vomiting, odema, bleeding, lethargy, and liver enlargement.

Other common pain relievers, including aspirin, ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve) should be avoided as they can increase the risk of bleeding complications.

[72] Infections are most commonly acquired in urban environments where the virus is primarily transmitted by the mosquito species Aedes aegypti.

[71] The first historical record of a case of probable dengue fever is in a Chinese medical encyclopedia from the Jin dynasty (266–420) which referred to a "water poison" associated with flying insects.

[79][81] It is assumed that dengue was constantly present in many tropical urban centres throughout the 19th and early 20th centuries, even though significant outbreaks were infrequent.

The severe hemorrhagic form of the disease was first reported in the Philippines in 1953; by the 1970s, it had become recognised as a major cause of child mortality in Southeast Asia.

[85][86] The term break-bone fever was applied by physician and United States Founding Father Benjamin Rush, in a 1789 report of the 1780 epidemic in Philadelphia, due to the associated muscle and joint pains.

[86] Terms for severe disease include "infectious thrombocytopenic purpura" and "Philippine", "Thai", or "Singapore hemorrhagic fever".

[86] Research directions include dengue pathogenesis (the process by which the disease develops in humans), as well as the biology, ecology and behaviour of the mosquito vector.

[90] Rising temperatures and altered rainfall patterns are expanding the season and habitats of Aedes mosquitoes, the primary vectors of the disease.

[91] In India, a study has developed an early warning system that analyzes regional climate factors—such as temperature, rainfall, and humidity—to predict potential dengue outbreaks two months in advance, enhancing preparedness and response strategies.

[95] Goals are to increase public awareness about dengue, mobilize resources for its prevention and control and, to demonstrate the Southeast Asian region's commitment in tackling the disease.