Impacts of alien species on human health have recently become a major issue in medical research and invasion ecology, but comprehensive assessments of this subject are largely lacking. Here, we provide a literature review of alien species with public health impacts in Europe based on a systematic search in the Thomson Reuters Web of Science. We detected 77 relevant articles, of which 21 were reviews and 56 were original research articles. The taxonomic focus was on vascular plants (n=31 articles) and dipterans (n=25 articles). The original research articles mainly covered the spread of the study species, while early invasion stages (introduction, establishment) as well as impact and management were less investigated. Alien species of health concern in Europe are mostly introduced as contaminants, and mostly originate from climatically similar regions of the Northern Hemisphere. In those cases (36% of all articles) when information on the trend in range and abundance was provided, this trend was mostly increasing. We detected little information on the severity of the impacts (two articles) and the interaction with climate change (three articles). In 15 original articles (28%) specific management measures were suggested, in only one article the socioeconomic costs were assessed. We conclude that European research on human health impacts of alien species is biased towards few species, and that several important aspects such as early invasion stages, severity of impact and its temporal trends, and the scale of the socioeconomic costs caused are poorly understood. Interdisciplinary projects bridging gaps between ecologists medical researchers, socioeconomists and public health authorities are required to link alien species to severity and trends of impacts, which is a crucial requisite for risk assessment and decision making.

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Background: Alien species are frequently considered a serious environmental threat but negative impacts on human health through injury, allergy, or as vectors of disease sometimes have the most dire consequences for human livelihoods. Climate change and the increasing magnitude and frequency of introductions of species across geographic barriers as a result of international trade are likely to change their establishment, spread, abundance, physiology or phenology, potentially also altering their human health impacts. Yet despite receiving increasing attention in the scientific literature, there have been few attempts to quantify recent changes in human health impacts. Here we report the findings from a systematic map of the literature identifying evidence of any change in the occurrence, frequency or severity of impacts of alien species on human health in Europe over the last 25 years. Methods:We conducted a systematic search of the ecological and medical literature using English language search terms to identify potentially relevant studies. Search results were assessed against inclusion criteria published in an a priori protocol at title, abstract and full-text to determine their suitability for inclusion in the review. Repeatability was checked at each stage by comparing a subset between reviewers and testing for inter-rater agreement using Cohen's kappa test. Studies deemed relevant at full text were coded against bibliographic, inclusion and study design criteria to create a searchable database of evidence. Results:Searches retrieved over 15,700 results yet only sixteen cases met criteria for inclusion in the systematic map. Most of this evidence represents first records of impacts from different areas, and in particular first reports of transmission of exotic diseases by introduced mosquito species. Conclusions:There is currently limited published evidence demonstrating a change in the occurrence, frequency or severity of human health impacts caused by alien species in Europe over the last 25 years. Relevant studies relate to only a few species, often report specific cases and rarely link health impacts with ecology, distribution or spread of the species. Difficulties in attributing human health impacts, such as stings or allergies, to a specific alien species likely complicate attempts to measure changes, as may differences in professional interests between the environmental and health professions. Future studies could helpfully compare spread or abundance with reported, rather than potential, health impacts. Better cooperation between invasion ecologists and health professionals working in affected areas are likely to be necessary to improve the evidence base on this topic for the future.