Dengue Symptoms: Knowing exactly what dengue's signs and symptoms are? The primary symptoms of dengue are high fever, severe headache, muscle and joint pains. Dengue virus can vary in severity from mild acute febrile illness to a fatal infection. In most people the symptoms of dengue fever start within 4 to 7 days of bite of an infected mosquito. Generally, younger children have a milder illness than older children and adults. Read articles and information on dengue fever symptoms in children as well as adults.