Climate change and infectious diseases: a general overview

It is well accepted that infectious diseases are climate-sensitive; however, the extent of human vulnerability is still poorly elucidated as numerous biological, ecological, environmental, and social factors act all together with complex interactions contributing to the spreading of infectious diseases and producing different effects in different social-economic and geographical contexts. Climatic changes can affect the host and pathogens relationship in different ways both during extreme weather events and during everyday life. Climatic conditions are becoming more suitable for travel-imported and local transmission of climate‑sensitive infectious diseases, including water or vector borne pathogens, such as dengue, chikungunya, West Nile virus, malaria, vibrio species. Different climatic hazards strengthen pathogens by enhancing suitability for reproduction, virulence, accelerating the life cycle, increasing seasons/length of likely exposure, enhancing pathogen-vector interactions. Further, climate change can diminish human capacity to cope with pathogens by affecting human immunocompetence to disease due to altered body conditions, malnutrition, stress or traumas, unsafe living conditions or reduced access to medical care. Consequences can be especially serious in most vulnerable subgroups, such as pregnant women, children, elderly, people in poor health, specific workers. Recently, a systematic review showed that worldwide 58% of infectious diseases have been at some point aggravated by climatic hazards and revealed more than 1,000 unique pathways by which climatic hazards, via different transmission types, can affect disease spread and human health. Further research is, therefore, needed to better elucidate the major climate-related drivers in different social and territorial contexts to plan and implement effective local public health actions to prevent or mitigate the spread of climate-sensitive infectious diseases.