Marked increase in cryptosporidiosis cases, Spain, 2023.

BackgroundBy mid-September 2023, several event notifications related to cryptosporidiosis had been identified from different regions in Spain. Therefore, a request for urgent notification of cryptosporidiosis cases to the National Surveillance Network was launched.AimWe aimed at assessing the extent of the increase in cases, the epidemiological characteristics and the transmission modes and compared to previous years.MethodsWe analysed data on case notifications, outbreak reports and genotypes focusing on June-October 2023 and compared the results to 2016-2022.ResultsIn 2023, 4,061 cryptosporidiosis cases were notified in Spain, which is an increase compared to 2016-2022. The cumulative incidence was 8.3 cases per 100,000 inhabitants in 2023, sixfold higher than the median of 1.4 cases per 100,000 inhabitants 2016-2022. Almost 80% of the cases were notified between June and October. The largest outbreaks were related to contaminated drinking water or swimming pools. Cryptosporidium hominis was the most common species in the characterised samples (115/122), and the C. hominis IfA12G1R5 subtype, previously unusual in Spain, was detected from 76 (62.3%) of the 122 characterised samples.ConclusionsA substantial increase in cryptosporidiosis cases was observed in 2023. Strengthening surveillance of Cryptosporidium is essential for prevention of cases, to better understand trends and subtypes circulating and the impact of adverse meteorological events.