Waterborne protozoan outbreaks: An update on the global, regional, and national prevalence from 2017 to 2020 and sources of contamination

The aim of this review is to identify the worldwide trend of waterborne protozoan outbreaks and how it varies between geographic regions during the period from 2017 to 2020. Data about waterborne protozoan outbreaks were gathered and stratified by continent, country, water source, and protozoan species associated with the out-break. The highest prevalence of waterborne protozoan outbreaks was reported in developed countries. Out of 251 outbreaks reported worldwide during the studied period, 141, 51 and 24 outbreaks were recorded in the USA, UK, and New Zealand, respectively. These outbreaks were mainly associated with Cryptosporidium (192 out-breaks) and Giardia (48 outbreaks). Cyclospora cayetanensis, Dientamoeba fragilis and Toxoplasma gondii were as-sociated with 7 outbreaks. One outbreak was associated with each of Blastocystis hominis, Entamoeba histolytica, Microsporidia or Naegleria fowleri. This data suggests large discrepancies in the number of outbreaks reported be-tween geographic regions, with most outbreaks recorded in developed countries. Differences in the prevalence of outbreaks between countries are likely attributed to the availability of diagnostic capabilities and surveillance programs to monitor water contamination with pathogenic protozoa. More attention and concerted efforts are required to improve water safety and to alleviate the impact of waterborne protozoan infections. Appropriate surveillance of water contamination with protozoa can enable public health officials to identify source of contam-ination and implement the necessary measures to limit transmission and prevent outbreaks. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The review highlights a higher prevalence of waterborne protozoan outbreaks in developed countries, particularly associated with Cryptosporidium and Giardia. Variations in the number of outbreaks between geographic regions are likely attributed to differences in diagnostic capabilities and surveillance programs for monitoring water contamination.