Epidemiology of Clonorchis sinensis infection in Guangdong, China, 2006–2024: a retrospective analysis of over 0.17 million reported cases from passive surveillance data

Clonorchiasis, caused by the ingestion of raw freshwater fish containing Clonorchis sinensis metacercariae, lacks national notifiable status in China, resulting in insufficiently characterized epidemiology. However, as an important endemic disease in Guangdong province, it is reported in the National Notifiable Disease Reporting System (NNDRS). We conducted an observational study to characterize clonorchiasis epidemiology using NNDRS data from Guangdong. Cases included in this study were patients diagnosed with clonorchiasis in Guangdong province (2006–2024) and reported via NNDRS. Proportion and reported incidence of cases by gender, ages, and occupations were analyzed and compared, when spatial analysis was employed to identify high clusters at county level. There were 170,709 cases reported during the study period, of which 166,728 cases lived in Guangdong. A steady increase in reported incidence from 1.77/100,000 in 2006 to 37.27/100,000 in 2024 was observed (average annual percent change (AAPC):17.22%, P <0.001). The median age of patients was 54.0 years (inter-quartile range, 44.0–64.0). Most cases were male (78.30%). House-hold or unemployed personnel (25.86%), retirees (20.43%) and farmers (16.66%) comprised the majority. The reported incidence was notably higher among males and individual aged 65–69 years. Although clonorchiasis was reported in all 21 prefecture-level cities, spatial clustering was observed, particularly in the developed Pearl River Delta region. Our findings revealed the importance of clonorchiasis as a public health problem in Guangdong province. Precise strategies for prevention and control of clonorchiasis should be employed for targeted populations, with an emphasis on middle-aged and elderly people, male individuals, and people living in Pearl River Delta region.