[Characteristics on the onset features of scarlet fever in Beijing, 2006-2015].

Objective: This study aimed to explore the incidence trends and onset features of scarlet fever during the years of epidemic, from 2006 to 2015, in Beijing. Methods: Spatial, temporal and population distributions, prognosis of the reported cases and surveillance data on scarlet fever and other streptococcal infections (including the patients of streptococcal infection, tonsillitis and isthmitis) were analyzed by the descriptive epidemiological methods. Results: A total of 27 987 scarlet fever cases were reported from 2006 to 2015, with the incidence rates as 7.04 to 18.53 per 100 000 persons during these years, except for 2011. A total of 6 152 cases were reported in 2011, with the incidence of 31.37 per 100 000 persons, significantly higher than the average levels of the other years. There were more cases reported in rural-urban continuum, in summer and winter, with most of the cases were children in primary schools and infant-institutes. From May to December in 2011, 4 332 cases were interviewed three weeks after the disease onset, and their conditions improved or recovered, with no death or complication appeared at the follow-up period. There were 2 725 cases of scarlet fever and 104 013 clinical cases of streptococcal infections reported in 36 surveillance hospitals during the same period. The ratio between numbers of scarlet fever cases and streptococcal infection was 1 ∶ 38.17. The weekly numbers of scarlet fever were remarkably correlated to the streptococcal infections, with a Pearson's correlation coefficient as 0.729 (P<0.001). Accordingly, we estimated that about 21.4 thousand clinical cases of streptococcal infections that were caused by Group A streptococcus in 2011, in Beijing. Conclusions: Incidence of scarlet fever in 2011 was significantly higher than the average levels of other years in Beijing, but characteristics on spatial, temporal and population distributions of scarlet fever remained the same, with good prognosis of the reported cases. A large number of culture-positive Group A streptococcus infections among all the clinical cases of streptococcal infection might have been served as important source on septic infection, of scarlet fever.