[Analysis on epidemiological characteristics of anthrax public health emergencies in China, 2004-2023]

Objective: To analyze the epidemiological characteristics of public health emergencies caused by anthrax in China from 2004 to 2023, and provide scientific evidence for the improvement of targeted anthrax prevention and control measures. Methods: The data were derived from the reports of anthrax public health emergencies and case reporting cards of infectious diseases in China Disease Prevention and Control Information System from January 1, 2004 to December 31, 2023, and χ² test was used to compare the differences between groups. Software Joinpoint 5.3.0 was used for trend analysis on the reported incidence of anthrax and the count of reported public health emergencies by using the piecewise linear regression model. Results: From 2004 to 2023, a total of 169 public health emergencies caused by anthrax were reported nationwide, with a case fatality rate of 2.63% (23/874). The reported case count M(Q₁, Q₃) for each public health emergency was 3 (2,6) cases. The reported incidence rate of anthrax showed an overall downward trend from 2004 to 2023 [average annual percentage change (AAPC)= -2.56%, P=0.030], and an upward trend after 2012 [annual percentage change (APC)=4.23%, P=0.010]. The reported public health emergency count showed an overall upward trend (AAPC=1.28%, P=0.647), especially after 2013 (APC=15.91%, P=0.001). The proportions of grade A emergencies (with 1 - 5 cases) and emerging/re-emerging public health emergencies of anthrax increased from 63.04% (29/46) and 4.35% (2/46) during 2004-2008 to 85.48% (53/62) and 25.81% (16/62) during 2019-2023, respectively. Anthrax cases were mainly cutaneous anthrax ones (85.80%, 145/169). The proportion of local anthrax epidemics caused by the breeding, slaughtering or transaction of sick or dead livestock was 95.27% (161/169), and the proportion of imported anthrax epidemics caused by cross-regional transportation/transaction of sick or dead livestock was 4.73% (8/169). The annual incidence peak was during July-September (73.37%, 124/169). Both the anthrax cases and related public health emergencies showed increasing trends in eastern and central China. The cases were mainly men (82.19%, 586/713), those aged 31-60 years (70.95%, 425/599), and farmers/herdsmen (80.51%, 471/585). From 2019 to 2023, the proportions of the cases in slaughterhouse workers and people being engaged in livestock trade increased from 4.07% (20/491) and 1.22% (6/491) to 24.46% (23/94) and 9.57% (9/94) respectively (χ²=48.28, P<0.001; χ²=45.63, P<0.001). Conclusions: From 2004 to 2023, anthrax presented a low-level epidemic pattern in China. The risk of transmission caused by long-distance livestock trade increased. The areas affected gradually expanded from western regions to the eastern and central regions. The risk of transmission in slaughterhouse workers and people being engaged in livestock trade gradually increased. It is suggested to strengthen the quarantine of animals and feed products across regions to reduce the risk of cross-regional transmission, improve the sick livestock supervision and further conduct health education about anthrax prevention and control.