Dengue is a viral infection transmitted to humans through the bite of Aedes mosquitoes, primarily Aedes aegypti. It is caused by one of four closely related viruses (DENV-1, DENV-2, DENV-3, DENV-4), which means a person can be infected up to four times in their lifetime. Dengue is most common in tropical and subtropical regions, including parts of Asia, Africa, and the Americas.

The disease manifests with flu-like symptoms, including sudden high fever, severe headache, pain behind the eyes, joint and muscle pain (sometimes referred to as "breakbone fever"), rash, nausea, and vomiting. In severe cases, dengue can progress to dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), both of which can be life-threatening due to bleeding, blood plasma leakage, and organ failure.

There is no specific antiviral treatment for dengue; management focuses on supportive care, including rest, fluids to prevent dehydration, and pain relievers like acetaminophen (avoiding aspirin or ibuprofen, which can increase the risk of bleeding). Preventive measures include controlling mosquito populations and protecting against mosquito bites using repellents, wearing long-sleeved clothing, and sleeping under mosquito nets. In some countries, a vaccine (Dengvaxia) is available, but it is recommended only for individuals who have already been exposed to the dengue virus.