To the Editor: In his Perspective article on rheumatic heartdisease in developing countries, Carapetis (Aug. 2 issue)1 correctlynotes the important contribution of improved living conditionsto the decline in the incidence of acute rheumatic fever overrecent decades in wealthy countries. However, he does not acknowledgethe contribution of the very substantial decrease in the prevalenceof highly rheumatogenic emm types of group A streptococci ascausative agents of acute pharyngitis.
Our surveillance studies of pediatric pharyngitis group A isolatesin the United States and Canada from 2000 through 2005 showeda striking disappearance of emm types 14, 18, 19, and 29 ora marked decrease of emm types 3, 5, and 6. These have beenthe most important rheumatogenic types from the 1960s (whenrheumatic fever was prevalent) to the present decade (when rheumaticfever is quite rare).2 The basis for this marked decline incirculating rheumatogenic types is not clear, but it is verylikely to be independent of the changes in living conditions.
Stanford T. Shulman, M.D. Northwestern University Feinberg School of Medicine Chicago, IL 60611 sshulman{at}northwestern.edu
References
Carapetis JR. Rheumatic heart disease in developing countries. N Engl J Med 2007;357:439-441. [Free Full Text]
Shulman ST, Stollerman G, Beall B, Dale JB, Tanz RR. Temporal changes in streptococcal M protein types and the near-disappearance of acute rheumatic fever in the United States. Clin Infect Dis 2006;42:441-447. [CrossRef][Web of Science][Medline]
The author replies: It may well be that changes in the virulenceof circulating group A streptococci have accounted for muchof the decline in the incidence of rheumatic fever since thelate 1960s in the United States. However, approximately 95%of the reduction in the rate of death due to rheumatic feverduring the 20th century in the United States occurred before1960,1 probably because of reduced group A streptococcal transmissionresulting from an improved housing infrastructure.
I agree with the concept of "rheumatogenic" group A streptococci,but studies in areas where rheumatic fever is common have notshown associations with classic rheumatogenic emm types.2,3In these settings, rheumatogenic strains, regardless of theemm type, are probably always circulating — hence theendemic rather than epidemic disease pattern.4 In populationsin which dozens of streptococcal strains are present at anyone time,5 dramatic reductions in overall transmission rateswill be necessary before we can expect to see a waning of particularrheumatogenic strains.
Jonathan R. Carapetis, Ph.D. Menzies School of Health Research Casuarina, NT 0811, Australia jonathan.carapetis{at}menzies.edu.au
References
Gordis L. The virtual disappearance of rheumatic fever in the United States: lessons in the rise and fall of disease: T. Duckett Jones Memorial Lecture. Circulation 1985;72:1155-1162. [Free Full Text]
Martin DR, Voss LM, Walker SJ, Lennon D. Acute rheumatic fever in Auckland, New Zealand: spectrum of associated group A streptococci different from expected. Pediatr Infect Dis J 1994;13:264-269. [Web of Science][Medline]
Pruksakorn S, Sittisombut N, Phornphutkul C, Pruksachatkunakorn C, Good MF, Brandt E. Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in northern Thailand. J Clin Microbiol 2000;38:1250-1254. [Free Full Text]
Carapetis JR, Currie BJ, Kaplan EL. Epidemiology and prevention of group A streptococcal infections: acute respiratory tract infections, skin infections, and their sequelae at the close of the twentieth century. Clin Infect Dis 1999;28:205-210. [Web of Science][Medline]
McDonald MI, Towers RJ, Andrews RM, et al. The dynamic nature of group A streptococcal epidemiology in tropical communities with high rates of rheumatic heart disease. Epidemiol Infect (in press).
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