Circular distribution analysis on seasonality of hand, foot, and mouth disease in Dongcheng district of Beijing

Objective To analyze the time distribution characteristics of hand, foot, and mouth disease (HFMD) in Dongcheng district of Beijing, so as to provide supports for the prevention and treatment of HFMD. Methods The monthly incidence data of HFMD cases with current addresses within Dongcheng district from 2010 to 2018 were sorted out from the disease surveillance information reporting management system according to the dates of onset. The concentration ratio and circular distribution index were used to analyze the trend of clustering in dates of onset of HFMD. The Rayleigh test was used to test the existence of the average angle. Results A total of 5 958 cases were reported in Dongcheng district from 2010 to 2018, with an average annual incidence of 68.28/100,000. For the clustering analysis, the concentration ratio (M) was 0.52 and the average angle () was 195.31° while the incidence peak of HFMD was on July 18 and the peak period was from May 28 to September 6. Different peak dates, length as well as the start and end dates of peak period were observed in each year. Conclusions The incidence of HFMD showed obvious seasonality characteristics. The peak period of incidence was mid-July. The concentration ratio and circular distribution can describe the seasonal epidemic characteristics of HFMD. Key words: Hand, foot, and mouth disease; Circular distribution; Concentration ratio