Impact of the COVID-19 restrictions on the epidemiology of Cryptosporidium spp. in England and Wales, 2015-2021: a time series analysis.

In England and Wales, cryptosporidiosis cases peak in spring and autumn, associated with zoonotic/environmental exposures ( spring/autumn) and overseas travel/water-based activities ( autumn). Coronavirus disease 2019 (COVID-19) restrictions prevented social mixing, overseas travel and access to venues (swimming pools/restaurants) for many months, potentially increasing environmental exposures as people sought alternative countryside activities. COVID-19 restrictions reduced incidence of cases and potentially increased incidence of cases. To inform/strengthen surveillance programmes, we investigated the impact of COVID-19 restrictions on the epidemiology of and cases. Cases were extracted from the Cryptosporidium Reference Unit (CRU) database (1 January 2015 to 31 December 2021). We defined two periods for pre- and post-COVID-19 restrictions implementation, corresponding to before and after the first UK-wide lockdown on 23 March 2020. We conducted a time series analysis, assessing differences in and incidence, trends and periodicity between these periods. There were 21 304 cases (=12 246; =9058). Post-restrictions implementation incidence of dropped by 97.5 % (95 % CI: 95.4-98.6 %; <0.001). The decreasing incidence trend pre-restrictions was not observed post-restrictions implementation due to lack of cases. No periodicity change was observed post-restrictions implementation. There was a strong social gradient; there was a higher proportion of cases in deprived areas. For , post-restrictions implementation incidence fell by 49.0 % (95 % CI: 38.4-58.3 %; <0.001). There was no pre-restrictions incidence trend but an increasing incidence trend post-restrictions implementation. A periodicity change was observed post-restriction implementation, peaking 1 week earlier in spring and 2 weeks later in autumn. The social gradient was the inverse of that for . Where recorded, 22 % of and 8 % of cases had travelled abroad. cases almost entirely ceased post-restrictions implementation, reinforcing that foreign travel seeds infections. incidence fell sharply but recovered post-restrictions implementation, consistent with relaxation of restrictions. Future exceedance reporting for should exclude the post-restriction implementation period but retain it for (except the first 6 weeks post-restrictions implementation). Infection prevention and control advice should be improved for people with gastrointestinal illness (GI) symptoms to ensure hand hygiene and swimming pool avoidance.