Occurrence and spread of the streptococcal organism are influenced by the age of the patient, seasonality and socio-economic conditions. A superimposed genetic predisposition also probably exists ( Guilherme 1991 ; Olmez 1993 ). Supporting evidence for an underlying immunological susceptibility for developing acute rheumatic fever is found in the higher antibody response observed in rheumatic patients compared with non-rheumatic individuals following administration of influenza vaccine, and the finding of isologous red blood cells in these patients ( Barrett 1984 ). A non-HLA B cell antigen, known as the D8/17 lymphocyte alloantigen, has also been identified in patients with rheumatic fever ( Ganguly 1992 ; Khanna 1989 ). A test to detect this B cell antigen marker can aid in the diagnosis of rheumatic fever and can help detect siblings who are at risk of developing the disease ( Herdy 1992 ).