Which disease is characterized by high fever and severe headache, caused by a virus?

Dengue fever is characterized by high fever and severe headache, and it is specifically caused by the dengue virus, which is transmitted primarily by Aedes mosquitoes. After the initial infection, dengue can cause a range of symptoms, and often presents with a sudden onset of high fever, severe headaches, pain behind the eyes, joint and muscle pain, and rash. The fever can be quite high, often reaching 104°F (40°C), which is significant for diagnosis.

In contrast, while illnesses like malaria and chikungunya can also present with fever and headache, malaria is caused by Plasmodium parasites, and chikungunya is associated with severe joint pain but is less prominently characterized by high fever and headache. Typhoid fever is caused by Salmonella typhi and typically presents with prolonged fever and gastrointestinal symptoms, rather than the acute symptoms associated with dengue. Thus, the features of high fever and severe headache align most closely with dengue fever as the correct answer.