There is evidence of the need for T-cell and antibody-mediated control.7 In the case of S. Typhi infection, up to 20% of infected individuals may have recurring infection until a protective state is eventually attained, or they go on to relapse.8,9 There is only a partial picture of the nature of CD4 T-cell immunity during Salmonella infections and the identity of the key Salmonella T-cell antigens is unknown. The gene discussed is CD4; the disease is infection.