Epydemiologic study of an outbreak of scarlet fever

Aim: Report on the epidemiology of scarlet fever. Methods: A description is made of the cases of scarlet fever recorded among a pediatric population in two health care centres between January 1996 and December 1997. Inclusion criteria were a clinical presentation compatible with scarlet fever, and the isolation of group A streptococci in pharyngeal exudate. Penicillin was the treatment of choice. Reactive strips were used to discard proteinuria. Pharyngeal cultures were made of the individuals cohabiting with the patients, and two samples were collected to study asymptomatic carriers in the school room where three cases of scarlet fever were detected. Positive cases were given antibiotics. Results: Thirteen patients (all under the age of 6 years) were diagnosed of scarlet fever (annual incidence 1,6%). All patients exhibited a tonsillar focus, and two suffered otitis media. The response to antibiotic treatment was favourable. There were no cases of rheumatic fever or glomerulonephritis. Two patients were subjected to tonsillectomy due to recurrence. Carrier positivity was 23,1% and 25,0%. Antibiotic treatment eradicated the streptococci. Group A streptococci were only isolated in 9,8% of the cohabiting individuals. Conclusions: Although streptococcal infections involving pharyngeal foci are more common after the age of 6 years, the children in the present study were younger. It seems reasonable to not perform control cultures in patients who have been adequately treated and remain asymptomatic, or in cohabiting relatives who show no symptoms. Up to 20% of children may be nasopharyngeal carriers of group A streptococci (30% in school outbreaks), in agreement with the results of the present study.