Dengue fever is a mosquito-borne viral disease caused by any of four dengue viruses. It is transmitted by the bite of an infected Aedes mosquito. An estimated 390 million dengue infections occur worldwide each year, especially in tropical areas of Southeast Asia, South America, and the Caribbean. Symptoms include high fever, severe headaches, joint and muscle pain, and skin rash. There is no vaccine to prevent dengue fever, so protection involves preventing mosquito bites by wearing protective clothing and using insect repellent. Treatment focuses on relieving symptoms and maintaining fluid balance, with medical care needed in severe cases to prevent complications like bleeding and shock.