Annual number of days suitable for Vibrio infections in the Baltic region. Source: Watts, N., et al., 2021, ‘The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises’, The Lancet 397(10269), pp. 129-170 (DOI: 10.1016/S0140-6736(20)32290-X)

Health issues

Elevated water temperatures accelerate the growth rate of certain water-borne pathogens, such as Vibrio species, which act through two major exposure pathways: drinking-water and recreational water use. Vibrio infections can cause gastroenteritis through the consumption of contaminated seafood or the infection of wounds being directly exposed to Vibrio species present in coastal water. Vibrio infections are a major concern for public health because these wound infections are potentially serious and can result in septicaemia and death. Other water-borne and food-borne diseases of relevance for Europe include campylobacteriosis, salmonellosisinfections with toxin-producing E. coli bacteriaLegionnaires’ disease, shigellosisleptospirosis, giardiasiscryptosporidiosis. Furthermore, high air temperatures can adversely affect food quality during transport, storage and handling more generally.
There is now also ecological evidence to suggest that increasing temperature is associated with increased antibiotic resistance for various pathogens, including Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. These data indicate that current forecasts of the public health burden of antibiotic resistance could be underestimated in the face of climate change.

Observed effects

Once a sea surface temperature (SST) threshold for Vibrio growth is reached at 15oC, there is a positive correlation between increasing SST and Vibrio concentrations in low salinity marine environments. Warming of the Baltic Sea is regarded as the main driver for the substantial increase in Vibrio infections in recent decades. The proportion of coastline suitable for Vibrio has increased by 61% compared to the 1980s baseline; 2018 and 2019 have seen the highest number of days with suitable conditions for Vibrio transmission and 100% of the Baltic coastline suitable during the hottest part of the year.

Projected effects

Infections caused by Vibrio have increased in the Baltic Sea and are expected to continue increasing due to climate change. SST suitability for Vibrio in the Baltic Sea is predicted to increase due to climate change during July, August, and September but even more so during the months immediately before and after the summer (June and October).
Climate change could also increase the risk of other water-and food-borne diseases, such as temperature-related salmonellosis and cryptosporidiosis, which are associated with extreme precipitation and flooding.

Policy responses

Regardless of climatic factors, health behaviour interventions and food safety regulations can reduce most negative consequences of climate change on water- and food-borne diseases.
The European Centre for Disease Prevention and Control has developed the Vibrio Map Viewer as an early warning system for public health, which is intended to help reduce human exposure to contaminated coastal waters. It monitors SST and salinity in the Baltic to provide alerts of elevated environmental suitability of Vibrio infections.


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