The correct answer is option 1, Dengue fever. Dengue fever is generally caused by viruses. Dengue fever is a mosquito-borne viral infection that is commonly found in tropical and subtropical regions. It is transmitted to humans through the bite of infected female mosquitoes, primarily the Aedes aegypti mosquito. The virus that causes dengue fever belongs to the Flaviviridae family and is specifically known as the dengue virus. Dengue fever is characterized by symptoms such as high fever, severe headache, joint and muscle pain, rash, and in severe cases can lead to dengue hemorrhagic fever or dengue shock syndrome, which can be life-threatening. It is important to note that options 2, 3, and 4 (Typhoid, Cholera, Tuberculosis) are caused by bacteria and not viruses.