Spatiotemporal scan statistic of scarlet fever in China, 2010−2019

  Objective   To understand the characteristics of scarlet fever's spatial and temporal distributions, as well as the clustering areas, in China from 2010 to 2019, and to provide evidence for scarlet fever prevention and control in China.

  Methods  Scarlet fever cases in 31 Chinese provinces (autonomous regions and municipalities) were collected from the Chinese notifiable infectious disease system between 2010 and 2019. The month is the time cluster unit, and the city is the minimum spatial unit.The spatial-temporal scan statistic was calculated with the software SaTScan 10.0.2, and the results were visualized with ArcGIS 10.7.

  Results  From 2010 to 2019, 596220 cases of scarlet fever were reported in China, with an annual incidence of 4.37 per 100 000 population. Scarlet fever incidence in China increased overall, with the lowest incidence of 1.62 / 100 000 in 2010 and the highest incidence of 6.04 / 100 000 in 2019. Two peaks were found in the annual temporal distributions in terms of incidence. The first peak occurred between May and June, and the second between November and December. Male cases accounted for 61.14% of the total number of cases. Scarlet fever was most common in children under the age of ten, accounting for 93.27% of the total incidence. The majority of scarlet fever cases were found in the Northeast. The main clusters of scarlet fever were found in the Northeast, North, and Northwest. The relative risk of scarlet fever has increased in cities adjacent to provinces with a high incidence of scarlet fever. Scarlet fever cluster areas have increased in the southern region, with the majority of them concentrated in economically developed cities and provincial capitals, including Shanghai, Shenzhen, Xiamen, Leshan, Dali, Lijiang, Hangzhou, Changsha, Chengdu, Kunming, Guiyang and other cities.

  Conclusion  Scarlet fever has grown more common in China since 2010. Children are more likely to be infected in summer and winter. The northern region had a higher incidence than the southern region. Scarlet fever is getting more common in southern China. Scarlet fever risk has increased in cities near high-incidence provinces. To stop the spread of scarlet fever, it is necessary to strengthen disease surveillance in kindergartens and primary schools, as well as investigate and deal with clustered epidemics in a timely manner.