CLINICAL SEVERITY OF RESPIRATORY SYNCYTIAL VIRUS GROUP-A AND GROUP-B INFECTION IN SYDNEY, AUSTRALIA

Respiratory syncytial virus (RSV) has two major antigenic groups, A an d B. There is disagreement as to whether or not there is a difference in the clinical severity of disease caused by the two RSV groups. This 3-year prospective study of infants and children with RSV-positive br onchiolitis examines the relative virulence of RSV Groups A and B and assesses the role that breast-feeding may have in modifying the clinic al severity of infection. Clinical severity was graded I (ventilated, severe), II (oxygen therapy, moderate), III (no ventilation or oxygen, mild). RSV serogrouping was performed. After exclusion of 60 subjects with known predisposing factors for severity, 444 infants and childre n were studied (Group A, 337; Group B, 107). The difference in proport ion of subjects with severity grade I and II with Group A compared wit h Group B infection was 6% (95% confidence interval, 4.7 to 16.7). For infants 0 to 6 months of age this difference was 5.6% (95% CI, 7.3 to 18.4). Nineteen cases were nosocomially transmitted. There was a pred ominance of Group A RSV infection but no difference in severity betwee n Group A and Group B infection.