Europe is facing a growing threat of tropical disease outbreaks, as rising temperatures linked to climate change cause illness brought by travellers.
This summer has seen a sharp spike in West Nile virus infections in Europe, following soaring temperatures, compared with the past 4 years.
Until the middle of August, 400 cases of the disease, which is carried by mosquitos, were recorded in Europe, with 22 fatalities, according to the European Centre for Disease Prevention and Control (ECDC). Countries affected include Italy, Greece, Hungary, Serbia and Romania.
‘We are all a bit taken aback about how fast these changes are coming down the pipeline,’ said Prof Jan Semenza, who leads on scientific assessment for the ECDC. ‘We are seeing more and more of these extreme weather events.’
‘Mosquitos and ticks are cold-blooded and are affected by higher temperatures. At higher temperatures, mosquitos replicate faster. Pathogens in the mosquito also replicate faster. Everything is speeded up and you get higher turnover, bigger populations of mosquitoes and a growing epidemic potential for viruses.’
The spike is due to an early start to the transmission season, caused by high temperatures followed by wet weather, conditions ideally suited to mosquito breeding, according to the World Health Organisation’s (WHO) regional office for Europe.
Last year, the Centres for Disease Control and Prevention found hotter temperatures, an increase in international travel and more people living near wildlife were linked to a rise in illness from mosquitos, ticks and flea bites in the US, including West Nile.
‘We wouldn’t say a particular outbreak is attributable to climate change, but we would say that climate change is making it easier to transmit these kinds of diseases,’ said Dr Diarmid Capbell-Lendrum, the WHO’s lead on climate change.
Climate change has had an unexpected effect on mosquitos and the transmission of diseases.
‘We know that mosquitos thrive in humid conditions and rainfall can increase breeding sites,’ says Rachel Lowe, an assistant professor in infectious diseases at the London School of Hygiene and Tropical Medicine.
‘But something we found recently is that drought conditions can also increase breeding, because of the ways people store water. We have this complicated, non-linear relationship.’