Monitoring of cryptosporidiosis: a shift in circulating Cryptosporidium hominis subtypes, the Netherlands, 2016 to 2024.

BACKGROUNDProtozoan parasites Cryptosporidium spp. are important causes of gastrointestinal disease. They can cause large outbreaks. In the Netherlands, cryptosporidiosis is not notifiable, and monitoring relies on voluntary laboratory reporting.AIMWe aimed to describe the epidemiology of human cryptosporidiosis in the Netherlands from 2016 to 2024 and investigate associations with subtype and meteorological variables.METHODSThree medical microbiology laboratories submitted faecal or DNA samples from patients with laboratory-confirmed cryptosporidiosis, with information about age and sex, for species identification and optional gp60 subtyping. Associations between numbers of infected patients and Cryptosporidium species, gp60 subtype, temperature and precipitation were analysed.RESULTSIn 2016-2024, 2,500 patients had laboratory-confirmed cryptosporidiosis, with a marked peak in 2023 (n = 622) caused by C. hominis. The lowest number of Cryptosporidium infections was recorded in 2021 (n = 61), with no C. hominis. Among all age groups, children aged ≤ 4 years had the highest number of infections (n = 493; 27%). In total, 1,166 (55%) patients had C. hominis and 951 (45%) had C. parvum infections. Infections with C. hominis peaked in September. We observed a weak association between temperature and the number of patients with C. hominis. Of the C. hominis identified, 207 were gp60 typed and an increase in subtype diversity was observed since 2022.CONCLUSIONIn the Netherlands, C. hominis drives the annual fluctuations in cryptosporidiosis. Continuous surveillance, including information about exposure to risk factors and molecular typing, is key to a better understanding of the underlying causes of Cryptosporidium spp. infections.