title: Temporal changes in streptococcal M protein types and the near-disappearance of acute rheumatic fever in the United States.
abstract: BACKGROUND
  The explanation for the very substantial decrease in the incidence of acute rheumatic fever in the United States, particularly over the past 50 years, is unclear. It has been proposed that certain M types of group A streptococci (GAS) include strains that are particularly rheumatogenic and that others are nonrheumatogenic.
  
  
  METHODS
  We compared the M type distribution of GAS recovered from children from Chicago, Illinois, with acute pharyngitis during 1961-1968 to that of GAS recovered from Chicago children and children from across the United States in 2000-2004, with attention to changes in M types that previously were associated with rheumatogenic strains.
  
  
  RESULTS
  The rheumatogenic types 3, 5, 6, 14, 18, 19, and 29 comprised 49.7% of 468 pharyngeal isolates during 1961-1968 but only 10.6% of 450 Chicago isolates during 2000-2004 (P < .001) and 17.9% of 3969 isolates nationwide during 2000-2004 (P < .001). Significant decreases in types 3, 5, and 6 and virtual disappearance of types 14, 18, 19, and 29 occurred between the 2 study periods. No change in the proportion of type 1 isolates, a highly heterogeneous group that includes some rheumatogenic strains, was observed. The nonrheumatogenic GAS types 2, 4, 22, and 28 increased from 4.9% to approximately 28% of pharyngeal isolates in Chicago and nationwide between the 2 study periods (P < .001).
  
  
  CONCLUSIONS
  These data support the concept of rheumatogenic strains of GAS and indicate that the marked decrease in the incidence of acute rheumatic fever in the United States over the past 4 decades is correlated with the replacement of rheumatogenic types by nonrheumatogenic types in cases of acute streptococcal pharyngitis in children. The reasons underlying the observed change in distribution of M types remain to be elucidated.
authors.affiliation: Division of Infectious Diseases, Children's Memorial Hospital, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA. sshulman@northwestern.edu
authors.forename: Stanford T
authors.initials: ST
authors.lastname: Shulman
authors.forename: Gene
authors.initials: G
authors.lastname: Stollerman
authors.forename: Bernard
authors.initials: B
authors.lastname: Beall
authors.forename: James B
authors.initials: JB
authors.lastname: Dale
authors.forename: Robert R
authors.initials: RR
authors.lastname: Tanz
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000942:Antigens, Bacterial / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D002641:Chicago / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005838:Genotype; D006801:Humans; D015994:Incidence; D010612:Pharyngitis / Q000453:epidemiology / Q000382:microbiology*; D015995:Prevalence; D012213:Rheumatic Fever / Q000453:epidemiology* / Q000382:microbiology; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D013997:Time Factors; D014481:United States / Q000453:epidemiology
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; C014689:streptococcal M protein