Background. Most invasive group A streptococcal (GAS) disease occurs sporadically. Reports of family clusters of these infections are scanty, and most invasive disease occurs in adults. We describe a family cluster of streptococcal toxic shock syndrome (STSS) involving 3 children and present the results of an epidemiologic investigation. Patients and Methods. During a 16-day period, 3 children in a family developed STSS with an interval of 7 and 9 days, respectively, between the onset of disease. Cases 2 and 3 had GAS isolated from blood culture. Case 2 was fatal. Pharyngeal culture survey of the family members and schoolchildren was conducted. Antibiogram, serotyping, detection of exotoxin genes, and random amplified polymorphic DNA patterns of the disease strains and survey strains were examined. Results. One of 15 family members sampled - the sister of the index case - and 7 (5.6%) of 125 schoolchildren sampled had GAS isolated from pharyngeal cultures. Of the 10 strains examined, 2 isolates from the patients, 1 from the sister of index case, and 2 from the classmates of case 2 (the fatal case) had an identical pattern of both genotype and phenotype. Conclusion. We describe a family cluster of STSS involving 3 children caused by a single clone and provide additional data regarding invasive GAS infection subsequent to household contact. Additional studies should be conducted in conjunction with surveillance to define better the magnitude of risk in household contacts and to identify settings in which subsequent infections may occur.
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