Epidemiological and environmental investigation of the ‘big four’ Vibrio species, 1994 to 2021: a Baltic Sea retrospective study

BackgroundThe <i>Vibrio</i> genus comprises several bacterial species present in the Baltic Sea region (BSR), which are known to cause human infections.AimTo provide a comprehensive retrospective analysis of <i>Vibrio</i>-induced infections in the BSR from 1994 to 2021, focusing on the 'big four' <i>Vibrio</i> species - <i>V. alginolyticus</i>, <i>V. cholerae</i> non-O1/O139, <i>V. parahaemolyticus</i> and <i>V. vulnificus</i> - in eight European countries (Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland and Sweden) bordering the Baltic Sea.MethodsOur analysis includes data on infections, <i>Vibrio</i> species distribution in coastal waters and environmental data received from national health agencies or extracted from scientific literature and online databases. A redundancy analysis was performed to determine the potential impact of several independent variables, such as sea surface temperature, salinity, the number of designated coastal beaches and year, on the <i>Vibrio</i> infection rate.ResultsFor BSR countries conducting surveillance, we observed an exponential increase in total <i>Vibrio</i> infections (n = 1,553) across the region over time. In Sweden and Germany, total numbers of <i>Vibrio</i> spp. and infections caused by <i>V. alginolyticus</i> and <i>V. parahaemolyticus</i> positively correlate with increasing sea surface temperature. Salinity emerged as a critical driver of <i>Vibrio</i> spp. distribution and abundance. Furthermore, our proposed statistical model reveals 12 to 20 unreported cases in Lithuania and Poland, respectively, countries with no surveillance.ConclusionsThere are discrepancies in <i>Vibrio</i> surveillance and monitoring among countries, emphasising the need for comprehensive monitoring programmes of these pathogens to protect human health, particularly in the context of climate change.