Dengue fever is caused by viruses transmitted by mosquitoes and is prevalent in tropical and subtropical regions. It causes symptoms like fever, headache, joint pains, and rash. There is no specific treatment other than rest and fluid intake, and aspirin or other anti-inflammatories should only be taken under doctor supervision. A more severe form is dengue hemorrhagic fever, which can cause shock. It requires close monitoring and fluid replacement, with blood transfusions sometimes needed to control bleeding. The mortality rate for dengue hemorrhagic fever ranges from 6-30%.