Dengue fever is a viral illness transmitted by Aedes mosquitoes, particularly Aedes aegypti and Aedes albopictus. It is common in tropical and subtropical regions of the world. The disease is caused by the dengue virus, which has four distinct serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), and infection with one serotype can provide lifelong immunity to that specific type, but not to the others. Symptoms: Dengue fever symptoms typically appear 4–10 days after being bitten by an infected mosquito and can range from mild to severe. Common symptoms include: High fever Severe headache Pain behind the eyes Joint and muscle pain Skin rash Nausea and vomiting Fatigue and weakness Mild bleeding (such as nosebleeds or gum bleeding) In severe cases, the infection can lead to dengue hemorrhagic fever or dengue shock syndrome, both of which can be fatal.