Epidemiological Characteristics of Anthrax and Bacillus anthracis Strains - China, 2020-2024.

INTRODUCTION: The incidence of anthrax in China has declined since 1990 but has resurged in recent years. The purpose of this study was to describe the epidemiology of anthrax and Bacillus anthracis (B. anthracis) in China from 2020 to 2024 to inform control strategies. METHODS: A descriptive analysis was performed of case characteristics. B. anthracis strains underwent whole-genome sequencing, and phylogenetic relationships were determined by core-genome single nucleotide polymorphism (cgSNP) and canonical single nucleotide polymorphism (canSNP) analysis. RESULTS: Between 2020 and 2024, 1,870 anthrax cases were reported, with a 0.59% case fatality rate. The majority of cases were cutaneous and the incidence increased from year to year. Cases were distributed across 12 provincial-level administrative divisions (PLADs), with most regions showing an increased incidence between 2021 and 2024. Farmers and herders were the most affected occupational groups, and farmers accounted for an increasing proportion of cases. Cases were primarily concentrated among young and middle-aged men and peaked between July and September. A total of 185 B. anthracis strains were identified in the 12 PLADs and were classified into four sublineages (A.Br.001/002, A.Br.Ames, A.Br.Vollum, and A.Br.005/006). A.Br.001/002 was the most prevalent and widely distributed sublineage. Phylogenetic analysis revealed 14 branches, demonstrating population diversity. Cross-clustering was present among strains from different PLADs. CONCLUSIONS: From 2020 to 2024, anthrax cases generally followed historical patterns but the incidence increased, with broader geographical spread, more diverse clinical types, and interprovincial transmission. These findings highlight the need to strengthen anthrax control efforts, particularly in the central and eastern PLADs.