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This special focus section of Virulence is dedicated to the topic of climate change and health. Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The rate of change is now faster than during any period over the past thousand years and it is expected to accelerate further in the upcoming years. But global warming is only part of the story. Earth system changes, such as changes in sea level, ocean circulation, the carbon cycle, the water cycle and more, are expected, challenging our species survival.1 It has been suggested that climate change could be the main global health threat of the 21st century.2
Establishing a causative relationship between climate change and alteration in the incidence and distribution of infectious diseases can be a challenging task, given the multivariate, interacting and non-linear causation of most diseases. Nevertheless, the literature contains numerous examples providing strong evidence that climate change has already affected the epidemiology of infectious diseases, especially the ones that are transmitted by insect vectors and through contaminated water. Hence, the effects of climate change have been established for several infectious diseases such as malaria,3 dengue fever,4 leptospirosis5 and cholera 6. Furthermore, extension of geographic distribution has been noted for several vector borne diseases including tick born encephalitis in Sweden,7 Chikungunya in the Americas,8 Lyme disease in Eastern Canada9 and malaria in East Africa.3 In addition multiple reports are suggesting that other types of community or nosocomial infectious diseases, caused by bacterial pathogens can exhibit seasonality and as such they may also be affected by climate change.10-13
This is considered a topic that has not received the deserved attention, especially among clinicians, even though they will be the front line responders to the health effects of climate change.
This section begins with an overview on climate change and heath, using an eco-social approach provided by Dr Maya Gislason.14 Human and natural systems cannot be considered independently. Diagnosis and containment of climate driven emerge of infectious diseases is the obvious task for the medical community. However this will not suffice. It is essential that the medical community contributes in capacity building for social and ecological systems and this can only be achieved through interdisciplinary collaborations, beyond health sciences.
A review on extreme weather events and infectious diseases outbreaks follows, expertly authored by late Anthony McMichael,15 internationally recognized for his pioneering work in environmental health, particularly in climate change and health. Extreme events have been witnessed historically as a result of natural climate variability. However, changing climate has resulted in changes in the frequency, intensity, duration and timing of extreme weather events with direct consequences on the epidemiology of certain infectious diseases.1 The paper by McMichael provides recent and historical examples of extreme weather events impacting on the epidemiology of infectious diseases and projects into the future.
The effect of climate change on migration and migrant health, with a special focus on infectious diseases is detailed by Dr Celia McMichael.16 Climate change has a direct effect on environmental systems and social conditions affecting food yields, water supply, population movements and migration patterns. It is estimated that the number of environmental migrants in the next decades will project in the tens to hundreds of millions leading to an increased risk for infectious diseases outbreaks due to poor access to sanitation, poor water and food quality. 17 Additionally, in the view of increased migration, health care systems will be challenged as existing service provisions have been developed for native populations and are often ill-equipped in providing accessible, appropriate and good quality services for migrants.
Developing responses to climate change requires actions beyond the scientific world as this institutes a public and political issue. Collaboration between different disciplines, including academics, policy makers and non-governmental organizations, is necessary in order to develop adaptation strategies and lessen health risks.18 Furthermore, even though the majority of greenhouse gas emissions are attributed to developed countries, it is the developing regions of the world that are affected the most by climate change.19 As such climate change should be viewed under the prism of social justice and effective adaptation in order to prepare and respond to the new evolving conditions will require collaborations among countries. The fundamental role of adaptation is discussed by Dr Ulisses Confalonieri.20
The final paper of this section relates to the new technologies available in global surveillance of emerging infectious diseases, reviewed by Dr Eirini Christaki.21 Systems of global surveillance are essential for the timely detection of outbreaks, the identification of syndromes caused by previously unknown pathogens and the rapid implementation of preventive and control measures. Effective surveillance is a challenge of outmost importance in under-sourced, developing countries with poor national public health systems, which are expected to be affected the most by climatic change.
Climate change, involving changes in mean climatic conditions and increased variability including extreme weather events, poses unprecedented health risks.22 There is widespread concern about the potential impact of global climate change on the distribution and burden of infectious diseases threats.1 In this special focus section of Virulence the authors through their thoughtful contributions have attempted to raise the attention to this significant subject that is frequently overlooked.