FIG 6 .

Different seasonalities of infections with sof-positive and sof-negative S. pyogenes strains. For the 1,442 isolates obtained in 2015, the data are based on the presence or absence of the sof gene. As shown, there is a disproportionate number of sof-positive isolates versus sof-negative isolates that is most evident in quarters 3. In 2012 to 2014, the presence or absence of sof was based solely on historic associations with the emm type or M serotype (13, 14). Because of differences in isolate collection from 2012 to 2015, the numbers of isolates shown (solid line) do not completely correlate with differences in disease incidence between different years. Rates per 100,000 population and surveillance populations are shown for each year.