The reported incidence of AHB in China declined from 7.52 per 100,000 in 2005 to 3.21 per 100,000 in 2019 (Mean=5.52), a 57.31% decrease. The annual number of reported cases in the primary, catch-up, and AHB surveillance pilot stages were 97,755, 77,520, and 58,396, respectively, and the annual incidences of AHB in the three stages were 7.45, 5.78, and 4.26 per 100,000. The annual incidence in the AHB surveillance pilot stage was 42.82% and 26.30% less than in the primary and catch-up stages. (Figure 1)
In the primary stage, there were 7 provincial-level administrative divisions (PLADs) with annual incidences over 10 per 100,000: Guangxi Zhuang Autonomous Region (22.18 per 100,000), Hainan Province (16.22), Gansu Province (14.97), Ningxia Hui Autonomous Region (14.12), Fujian Province (12.15), Inner Mongolia Autonomous Region (10.77), and Guizhou Province (10.30). In the catch-up stage, there were 5 PLADs with annual incidences over 10 per 100,000: Guangxi (21.72), Fujian (19.13), Hainan (12.12), Shanxi Province (10.92), and Xinjiang Uyghur Autonomous Region (10.39). In the AHB surveillance pilot stage, 1 PLAD had an annual incidence over 10 per 100,000: Guangxi at 14.72 per 100,000. (Figure 2)
During the primary stage, the 3 age groups with the highest annual incidence of reported AHB were aged 20−29 years old (14.35 per 100,000), 30−39 years old (9.75), and 40−49 years old (7.49). During the catch-up stage, the 3 age groups with the highest annual incidences were aged 20−29 years old (10.42 per 100,000), 30−39 years old (7.87) and 40−49 years old (6.41). In the AHB surveillance pilot stage, the 3 age groups with the highest annual incidence were aged 30−39 years old (5.89 per 100,000), 20−29 years old (5.77), and 50−99 years old (5.26). (Figure 3)
Compared with the primary stage, the 2 age groups with the largest decreases in annual incidence in the catch-up stage were aged 10–19 years old (a 52.29% decrease) and 0–9 years old (a 48.58% decrease). Compared with the catch-up stage, the 2 age groups with the largest decreases were aged 10–19 years old (a 55.02% decrease) and 20–29 years old (a 44.67% decrease). (Figure 3)
AHB affected males and females in all age groups. In the primary stage, there were 67,657 reported annual AHB cases among males (10.06 per 100,000 population) and 30,095 reported annual cases among females (2.29 per 100,000). In the catch-up stage, there were 52,223 reported annual AHB cases among males (7.60 per 100,000) and 25,297 reported annual cases among females (1.89 per 100,000). In the AHB surveillance pilot stage, there were 37,598 reported annual AHB cases among males (5.36 per 100,000) and 20,797 reported annual cases among females (1.52 per 100,000). (Figure 3)