Dengue Hemorrhagic Fever and Dengue Shock Syndrome are caused by infection of RNA Flavivirus transmitted by a mosquito vector. This test differentiates between Primary and Secondary infection. Paired acute and convalescent specimens that exhibit a significant change in titer are useful to confirm the clinical diagnosis of infection. NS1 antigen is a nonstructural protein found in infected patients from 1st day of fever up to 5 days after the onset of fever. A platelet count is a quick, common test that counts the number of platelets in your blood. Platelets are cells that help your blood clot. A low platelet count might be a sign of certain cancers or infections. A high platelet count can put you at risk for harmful blood clots or stroke.