[Incidence of Streptococcus pyogenes pharyngitis in Bariloche, Argentina]

The incidence and seasonality of pharyngitis by S. pyogenes in Bariloche, a city where long periods of low temperatures result in extended indoor activities were studied. A total of 5276 throat swab specimens collected during 2000-2003 in the clinical microbiology laboratories of the three main medical institutions of the city, were analyzed. Samples were cultured on blood-agar media containing 5% defibrinated sheep blood, and incubated for 24-48 h at 35 degrees C. Strains were identified using standard procedures. Monthly means for throat swabs, S. pyogenes isolates, and percent of S. pyogenes pharyngitis, were estimated. The incidence of pharyngitis by this microorganism was greater than 24% for every month within the April-December period, reaching a maximum in November (33%). February was the month with the lowest incidence (13%). It was observed an increasing trend since March through November with a through in July, and a marked decrease that began in December, reaching its lowest rate in January and February, the warmest months. This seasonal pattern differs from those observed for temperate climates. The incidence of S. pyogenes pharyngitis in Bariloche was high through the greater part of the year, since about the middle of autumn to the beginning of summer.