The Risks of Climate Change from Infectious Diseases

摘要

The World Health Organization has concluded that the climatic changes that have occurred since the mid-1970s could already be causing annually over 150,000 deaths and five million disability-adjusted life-years (DALY), mainly in developing countries. The less developed countries are, ironically, those least responsible for causing global warming. Many health outcomes and diseases are sensitive to climate, including: heat-related mortality or morbidity; air pollution related illnesses; infectious diseases, particularly those transmitted, indirectly, via water or by insect or rodent vectors; and refugee health issues linked to forced population migration. Yet, changing landscapes can significantly affect local weather more acutely than long-term climate change. Land-cover change can influence micro-climatic conditions, including temperature, evapo-transpiration and surface run-off, which are key determinants in the emergence of many infectious diseases. To improve risk assessment and risk management of these synergistic processes (climate and land-use change), more collaborative efforts in research, training and policy-decision support, across the fields of health, environment, sociology and economics, are required. Keywords: climate change, heat-related mortality, infectious diseases, morbidity, world health organization IntroductionGlobal climate change is expected to have broad health impacts. These could occur through various exposure pathways, such as the frequency or intensity of extreme heat waves, floods, and droughts. Warmer air temperatures could also influence local and regional air pollutants and aeroallergens. Less direct health impacts may result from climate-related alteration of ecosystems or water and food supplies, which in turn could affect infectious disease incidence and nutritional status. Finally, sea level rise could potentially lead to massive population displacement and economic disruption. Changes in temperature, humidity, rainfall, and sea level rise could all affect the incidence of infectious diseases. Mosquitoes, ticks, and fleas are cold-blooded and thus sensitive to subtle temperature and humidity changes. But vector-borne diseases are also dependent on many other interacting factors. Although there has been a resurgence of infectious diseases in recent years, it is unclear that climate change has played a significant role. Other factors such as the movement of human and animal populations, the breakdown in public health infrastructure, changes in land use, and the emergence of drug resistance have been contributory. The transmission of infectious diseases is strongly influenced by temperature, humidity, and rainfall. The distribution and seasonality of important infectious diseases are likely to be affected by climate change. Diseases transmitted by insect or rodent vectors have life cycles where much time is spent outside the human host, and therefore are more influenced by ambient conditions. There is a limited range of climatic conditions within which each such infective or vector species can survive and reproduce.