A group of viral diseases of diverse etiology but having many similar clinical characteristics; increased capillary permeability, leukopenia, and thrombocytopenia are common to all. Hemorrhagic fevers are characterized by sudden onset, fever, headache, generalized myalgia, backache, conjunctivitis, and severe prostration, followed by various hemorrhagic symptoms. Hemorrhagic fever with kidney involvement is HEMORRHAGIC FEVER WITH RENAL SYNDROME.