German and Swedish scientists have analyzed the patterns of distribution of Asian mosquitoes and the viral infections they carry in Europe and have concluded that dengue and chikungunya hemorrhagic fevers could become endemic in this part of the world. Climate change plays a major role in this. A report on the work was published in the journal Lancet Planetary Health.
Asian tiger mosquitoes (Aedes albopictus) are native to tropical and subtropical Asia. The arbovirus-borne diseases dengue and chikungunya are endemic there, but not in Europe. Ae. albopictus has spread rapidly around the world in the last half century due to globalization, urbanization, trade, tourism, and climate change. In Europe, it was first discovered in Albania in 1979, entered Italy in 1990, and has since become established in 21 countries and been introduced to six more. In its European habitats, this mosquito can transmit arboviruses in imported cases, causing local outbreaks of infection. The first such autochthonous outbreak of chikungunya fever in Europe, with 330 cases, occurred in Italy in 2007; similar outbreaks have now been reported in four European countries.
Jan Semenza (Umeå University, Heidelberg University) and colleagues conducted a systematic review of European Centre for Disease Prevention and Control and World Health Organization (ECDC/WHO) reports, technical reports and surveillance data, as well as peer-reviewed publications from PubMed, Scopus and Web of Science from January 1990 to October 2024 to find information on the distribution of Ae. albopictus and outbreaks of dengue and chikungunya. These data were used in a time-to-event analysis to follow the period from the establishment of the vector insect in a location to the occurrence of autochthonous outbreaks of infections in NUTS 3 regions.
The analysis was performed using single and multivariable regression, taking into account land use types, demographic and socioeconomic factors, imported cases and climate variables. It also included an analysis of recurrent outbreaks, stratification by warm and cold regions based on average summer temperatures below and above 20 degrees Celsius and forecasting the risk of outbreaks from the 2030s to 2060s under different climate change scenarios.
It was found that between 1990 and 2024, the interval between the first establishment of Ae. albopictus in NUTS 3 regions and the first outbreak of dengue or chikungunya fever decreased from 25 to less than five years. Over the same period, the interval between the first and second outbreaks in a region decreased from 12 years to less than a year. Regression analysis showed that favourable climatic conditions play a significant role in this process. Each degree Celsius increase in mean summer temperature was associated with an outbreak risk ratio of 1.55 (p < 0.0001) after adjusting for health funding, imported cases and land use type. First outbreaks were more common in warm regions than in cold ones (log-rank p = 0.088). The situation is expected to worsen significantly under climate change: under the highest greenhouse gas emissions scenario (SSP5–8.5), the number of dengue and chikungunya fever outbreaks in Europe is projected to increase almost fivefold by 2060 compared to the 1990–2024 level. The results indicate the need for serious mosquito control measures, enhanced surveillance, and early warning systems for outbreaks to prepare for the increasing risk of Ae. albopictus-borne disease endemicity in the European region, the authors conclude. Previously, American scientists conducted an empirical systematic study that showed that global climate change associated with greenhouse gas emissions increases the incidence of 58 percent of infectious diseases to some extent, while decreasing it in only 16 percent.
