The Arkray Widal S.Typhi Antigen Set H&O is a diagnostic reagent for the Widal test, which detects typhoid fever. It contains stained antigens derived from Salmonella Typhi (S. Typhi) strains, specifically the 'H' (flagellar) antigen and the 'O' (somatic) antigen, used to identify antibodies in patient serum through an agglutination reaction. The set provides uniform clumps with high sensitivity and accuracy, is available in different pack sizes and combinations.