A positive Widal's reaction developed in a 2-year-old girl following nontyphoid Salmonella gastroenteritis. Recent data from the Center for Disease Control suggest that false-positive Widal reactions following certain nontyphoid Salmonella infections may occur commonly. Antigens common to Salmonella groups A, B, and D account for this cross-reacting antibody.
Reynolds DW, Carpenter RL, Simon WH. Diagnostic Specificity of Widal's Reaction for Typhoid Fever. JAMA. 1970;214(12):2192-2193. doi:10.1001/jama.1970.03180120064016