Climate change fuelling mosquito-borne diseases in Europe

As many in the UK are gearing up for summer getaways, European countries are warning they are seeing rising cases of mosquito-borne diseases such as West Nile virus and dengue.

The European Centre for Disease Prevention and Control (ECDC) has said its latest figures show a continuing upward trend in the number of cases of dengue imported from dengue-endemic regions, as well as an increasing number of local outbreaks of West Nile virus infections and dengue within the EU/EEA.

In 2023, there were 130 locally acquired cases of dengue reported in the EU/EEA, and 71 cases were reported in 2022. This was a significant increase compared to the 10-year period 2010-2021, where the total number of locally acquired cases was 73 for the whole period, the ECDC said.

Imported cases are also on the rise with, 1,572 reported cases in 2022 and more than 4,900 cases in 2023. This was the highest number of imported dengue cases reported since the start of the surveillance at the EU level in 2008.

In the first months of 2024, several countries reported substantial increases in number of imported dengue cases, which could suggest that the numbers in 2024 might become even higher.

For West Nile virus, in 2023, EU/EEA countries reported 713 locally acquired human cases in 123 different regions of nine EU countries. Twenty-two of these regions were reported as places of infection for the first time in 2023; 67 deaths were also reported.

The mosquito Aedes albopictus, known for transmitting dengue, chikungunya, and Zika viruses, is spreading further north, east, and west in Europe, and now has self-sustaining populations across 13 EU/EEA countries, said the ECDC.

The mosquito Aedes aegypti, a carrier of yellow fever, dengue, chikungunya and Zika viruses, recently established itself in Cyprus.

It is widely anticipated that climate change will largely affect the spread of mosquito-borne diseases in Europe, for instance, through the creation of environmental conditions favourable for the establishment and growth of mosquito populations, the centre has also warned.

This year, a confirmed locally acquired human case of West Nile virus infection with onset of symptoms at the beginning of March was reported in Seville, Spain. Although an isolated case, it highlights that the transmission of West Nile virus can occur very early in the year, likely because of suitable climatic conditions.

The establishment of coordinated vector control measures is a key element for the fight against mosquito-borne diseases and further research will be needed to develop efficient but eco-friendly tools to manage mosquito populations, the ECDC recommended.

In parallel, simple measures such as removing stagnant water in gardens or balconies where mosquitos breed should be advertised to the population.

Personal protective measures to reduce the risk of mosquito bites include wearing clothes that cover most of the body, use of mosquito repellent, use of mosquito bed nets or window/door screens, and sleeping or resting in air-conditioned rooms. For these to be widely applied, effective awareness-raising campaigns among the general public are essential, the ECDC also emphasised.

Enhanced surveillance and early detection of travel-related and locally acquired cases of mosquito-borne diseases remain essential to implement timely and appropriate disease control measures, it recommended.

“Europe is already seeing how climate change is creating more favourable conditions for invasive mosquitos to spread into previously unaffected areas and infect more people with diseases such as dengue. Increased international travel from dengue-endemic countries will also increase the risk of imported cases, and inevitably also the risk of local outbreaks” said Andrea Ammon, ECDC director.

“Personal protective measures combined with vector control measures, early detection of cases, timely surveillance, further research and awareness-raising activities are paramount in those areas in Europe most at risk.”

Separately, the owner of South West Water has warned that global heating will increase the risk of outbreaks of the parasite that recently caused an outbreak of diarrhoea and vomiting in south Devon.

Pennon Group, in its annual Task Force on Climate-related Financial Disclosures report 2024, warned that “gradual and significant increasing average and high temperatures” could pose “risks to water quality and water treatment”, including the cryptosporidium parasite.

About 17,000 household customers of South West Water near the town of Brixham in south Devon were last month advised to boil their tap water before drinking it, after more than 100 people reported symptoms.

The Pennon report warned that rising temperatures and our changing climate would increase the likelihood of floods from rain and rising sea levels and lead to more heatwaves and storms, all bringing higher costs.

This could also bring with it risks to water quality, including “odour, discolouration, dissolved organics, cryptosporidium”, plus “increased microbe propagation and survivability” and increased invasive species, it added.