Ireland and other European countries need to prepare for the spread of mosquito-borne diseases across the Continent, the European Centre for Disease Control (ECDC) has warned.
Diseases such as dengue and West Nile virus that were previously considered tropical are now endemic across large parts of Europe, driven in part by climate change, it says.
While Ireland has not yet seen local transmission of mosquito-borne diseases, the number of cases is rising in many parts of southern Europe frequented by Irish holidaymakers, particularly France and Italy.
Climate change is contributing to the spread of mosquito-borne diseases in Europe through longer summers, more heatwaves and flooding episodes, according to Céline Gossner, ECDC principal expert in emerging and vector-borne diseases.
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As a result, she said, the breeding habitats of mosquitoes were moving further north. “Our concern is rising, as temperatures rise and flooding increases. Mosquitoes like warmth and water, so the risk they pose is increased.”
Asked whether Ireland could soon see local cases of dengue and West Nile fever, Ms Gossner said viruses “need to be introduced and you need the right bird population to sustain transmission”.
For now, Ireland was “far from the line of migration” of disease-bearing mosquitoes, though there had been cases in Germany and the Netherlands, she said. Southern Sweden is already making preparations for the arrival of these diseases.
The Culex pipiens mosquito that spreads West Nile virus is present in many parts of Ireland, though they have not been shown to carry infection.
If mosquito-borne diseases continued to spread, the security of Europe’s blood supply could be at risk, Ms Gossner warned. Given the diseases are spread through blood, people with symptoms cannot donate. However, infected people without symptoms can also transmit these viruses.
“If both viruses spread, there will be more deferrals and testing, a risk to blood supply and a financial cost,” she said. Even holidaymakers could be affected, as they have to defer blood donations if they spend any time in an outbreak area.
Dengue is present in 12 European countries – including the UK – and 177 regions, Ms Gossner told a press briefing at the ECDC headquarters in Stockholm. This compares with eight countries and 114 regions in 2014.
Sixty per cent of cases are in France and 30 per cent in Italy. This year, for the first time, Rome was affected, with 30 cases. Much further north, there were three cases in Paris. The spread of dengue would continue, Ms Gossner predicted, often along transport highways.
Increasing temperatures have raised the infectivity of mosquitoes by reducing the time that passes between successive transmissions of disease. They have also changed bird migration patterns, further aiding the spread of mosquito-borne diseases.
“And, when the weather is so hot, people tend to go out very early and very late in the day, exactly when most mosquitoes are most active.”
The creation of green space in cities to ameliorate the impact of heatwaves favoured the spread of mosquitoes, she said.
Most outbreaks of West Nile virus occur in the south of Europe, particularly Italy, Greece and Romania, but cases have also been recorded in Germany and the Netherlands. Of the 460 cases a year, 98 per cent are locally acquired. The best protection against these diseases was to prevent against being bitten, she said.
