The burden of group A streptococcal pharyngitis in Melbourne families.

BACKGROUND & OBJECTIVES: There are no recent data from industrialised countries documenting the incidence and costs of group A streptococcal (GAS) pharyngitis. Such data are important in developing policy regarding management (e.g., whether or not to use antibiotics to treat sore throat) and in planning preventive strategies, including preparing for the arrival of GAS vaccines. The present study was undertaken to estimate the incidence and costs of GAS pharyngitis in school aged children in Melbourne, Australia. We report here the results after initial 11 months of surveillance. METHODS: A total of 202 families (852 individuals) with at least one child aged 3 to 12 yr were enrolled across Melbourne in a family-based cohort study, and are being followed prospectively for 24 months. Surveillance data for acute GAS pharyngitis (including serology), throat carriage, and costs of the disease were collected. Additional cases of GAS pharyngitis have been ascertained to improve the precision of costing estimates. RESULTS: Cohort retention was 97 per cent. The spring, summer and winter carriage rates for children were 13.0, 8.0 and 16.0 per cent respectively. The incidence of GAS pharyngitis was 14 per 100 person-years for children. For every primary case there were 0.7 secondary cases and 24 per cent of families experienced at least one episode of GAS pharyngitis per year. Preliminary costing data suggest that 46 per cent of cases lead to school absenteeism and a high rate of antibiotic use. INTERPRETATION & CONCLUSION: The present data suggest that GAS pharyngitis remains very common in childhood, and that it has further implications in terms of secondary cases and costs.

Burden of acute sore throat and group A streptococcal pharyngitis in school-aged children and their families in Australia.

OBJECTIVE: The objective of this study was to determine the incidence, transmission, carriage, and risk factors for group A streptococcal pharyngitis in school-aged children and their families. METHODS: A 16-month, prospective, family-based cohort study was undertaken from August 2001 through December 2002 in Melbourne, Australia. A total of 202 families (853 people) with at least 1 child aged 3 to 12 years were randomly selected from 3 primary care practices across suburban Melbourne to collect surveillance data for acute group A streptococcal pharyngitis, including serology for index and secondary cases and intermittent carriage data. Cohort retention was 97% for 16 months. RESULTS: The incidence of acute sore throat, group A streptococcal swab-positive pharyngitis, and serologically confirmed group A streptococcal pharyngitis was 33, 13, and 8 per 100 child-years, respectively, for school-aged children (5-12 years) and 60, 20, and 15 per 100 family-years, respectively. Sore throat was less common in adults than children, but adults with sore throat were as likely as children to have group A streptococcal culture-positive or serologically proven pharyngitis. In families who had a primary case, 43% had at least 1 secondary case, and in family members who were at risk, 13% contracted a secondary case. The spring, summer, and winter carriage rates for children were 13%, 8%, and 16%, respectively, and for adults the rate was 2% across all seasons. CONCLUSIONS: Group A streptococcal pharyngitis is still common, and the peak incidence occurs in school-aged children. However, the incidence in adults is higher than expected, and the number of secondary cases in families may be an important factor when considering the potential benefits of treatment.

Strain prevalence, rather than innate virulence potential, is the major factor responsible for an increase in serious group A streptococcus infections.

BACKGROUND: It is postulated that the surge in incidence and severity of group A streptococcus (GAS) infections since the 1980s is due to the emergence of strains of GAS with increased virulence. We used active, population-based surveillance of invasive GAS disease, serologically confirmed pharyngitis, and carriage to determine whether particular strains were associated with invasive disease. METHODS: Two hundred twenty GAS isolates were collected--78 invasive, 34 pharyngitis, and 108 carriage. Isolates were characterized using emm typing, random amplification of polymorphic DNA (RAPD) profiling, and superantigen genotyping. RESULTS: emm1, emm12, and emm28 predominated in invasive disease and accounted for 30.8%, 12.8%, and 12.8% of all isolates, respectively. emm1, emm75, emm28, and emm4 were the most frequently isolated emm types in pharyngitis, and emm12 and emm1 predominated in carriage. emm12 was significantly associated with carriage rather than disease. There were no other significant associations between emm type and disease or carriage. There were no associations between any RAPD profile or superantigen genotype and invasive disease, pharyngitis, or carriage. One RAPD profile accounted for most cases of necrotizing fasciitis, which suggests that this strain might have particular features promoting connective-tissue infection. CONCLUSIONS: These data suggest that the emergence of GAS strains with increased virulence is not the main factor responsible for the surge in GAS-related infections. The prevalence of particular emm types, RAPD profiles, or superantigen genes in invasive disease may simply indicate widespread transmission of these strains in the population, rather than a particular ability to cause disease.

The epidemiology of invasive group A streptococcal disease in Victoria, Australia.

OBJECTIVE: To estimate the incidence and severity of invasive group A streptococcal infection in Victoria, Australia. DESIGN: Prospective active surveillance study. SETTING: Public and private laboratories, hospitals and general practitioners throughout Victoria. PATIENTS: People in Victoria diagnosed with group A streptococcal disease notified to the surveillance system between 1 March 2002 and 31 August 2004. MAIN OUTCOME MEASURE: Confirmed invasive group A streptococcal disease. RESULTS: We identified 333 confirmed cases: an average annual incidence rate of 2.7 (95% CI, 2.3-3.2) per 100,000 population per year. Rates were highest in people aged 65 years and older and those younger than 5 years. The case-fatality rate was 7.8%. Streptococcal toxic shock syndrome occurred in 48 patients (14.4%), with a case-fatality rate of 23%. Thirty cases of necrotising fasciitis were reported; five (17%) of these patients died. Type 1 (23%) was the most frequently identified emm sequence type in all age groups. All tested isolates were susceptible to penicillin and clindamycin. Two isolates (4%) were resistant to erythromycin. CONCLUSION: The incidence of invasive group A streptococcal disease in temperate Australia is greater than previously appreciated and warrants greater public health attention, including its designation as a notifiable disease.