Sustained heat raises infectious disease risks across Europe, ECDC warns

Longer and warmer summers are increasing the risk of several infectious diseases across Europe, the European Centre for Disease Prevention and Control (ECDC) has warned.

In a statement issued on July 29, the European Union health agency said that sustained higher temperatures, rather than individual heatwave episodes alone, were extending the periods during which pathogens and vectors could multiply or spread. Unlike a short heatwave, a prolonged warm spell gives mosquito populations more generations in which to build up and more time to acquire and transmit pathogens, which is why the agency is drawing this distinction.

The ECDC called for closer cooperation among countries and between public health, animal health and environmental authorities.

Here is what we know about the risks:

What is driving the increased risk?

Warmer temperatures can accelerate bacterial growth in food, increasing the risk of common foodborne illnesses during the summer, authorities say. The ECDC's food- and waterborne disease network tracks these seasonal increases across EU and EEA countries.

The ECDC advised people to wash fruit and vegetables, keep raw and cooked foods separate, cook food thoroughly and store it at safe temperatures.

What is vibriosis, and why is it spreading?

The agency also highlighted vibriosis, an infection caused by Vibrio bacteria.

According to the agency, the bacteria thrive in warm coastal waters with relatively low salinity, including parts of the Baltic Sea and river estuaries. Freshwater runoff from rivers and rainfall keeps salinity levels low in these areas, while summer warming rapidly raises water temperatures. Together, these factors create conditions in which the bacteria can thrive.

Infection can occur when an open wound is exposed to contaminated water or when contaminated seafood is consumed.

The ECDC has updated its Vibrio Viewer, which uses sea-surface temperature and salinity data to identify conditions suitable for the bacteria across five European sea regions.

The tool is updated daily and includes a five-day forecast, the agency said. It maps environmental suitability but does not predict an individual's risk of infection or incorporate data on human cases.

Why are mosquitoes and ticks a growing concern?

Longer warm and humid seasons are also allowing invasive mosquitoes to survive in areas where they were previously rare or absent, officials say.

This is increasing concerns about dengue, chikungunya and West Nile virus.

According to the latest available ECDC weekly West Nile report, 81 locally acquired human cases had been reported in Europe as of July 22.

The cases were recorded in Italy, Greece, North Macedonia, Romania, Spain and France, with 35 areas identified as affected.

Compounding these risks, milder conditions in spring and autumn are lengthening the period during which ticks remain active.

Infected ticks can transmit Lyme disease and tick-borne encephalitis, both of which can result in serious or long-term complications. A vaccine is available against tick-borne encephalitis.

What is being done, and what can people do?

The ECDC said its recent assessments had found that more than half of EU member states had adopted a national climate change adaptation plan.

It said that further work was required to ensure that specific measures were in place across different sectors to address the public health effects of extreme weather.

The agency recommended using insect repellent, wearing clothing that covers the arms and legs, installing window screens or mosquito nets, removing stagnant water from around homes and checking for ticks after spending time outdoors.

To reduce the risk of exposure to Vibrio bacteria, it advised people not to swim if they have open cuts, scratches or recent piercings, and recommended thoroughly cooking seafood sourced from affected waters.