Dengue viral (DV) infections affect all age groups causing asymptomatic infection however severe manifestations of shock and hemorrhage occurs in less than 5% of DV infections. Clinical manifestations include systemic and dynamic disease with a wide spectrum of clinical presentations ranging from mild to severe; however, the clinical evolution and outcome may be highly unpredictable. The course of illness is characterized by three phases like the febrile, critical and recovery phase. The most specific and life-threatening manifestation of the critical phase is an increase in capillary permeability leading to plasma leakage and rise in the hematocrit. Diagnostic methods involve serological tests, virological diagnosis and molecular methods. Warning signs are persistent vomiting, restlessness or lethargy, clinical fluid accumulation, mucosal bleeds along with rapid fall in platelet count. Treatment options and management are discussed in detail in the chapter.