雙重威脅：氣候變化和人畜共通傳染病

資料來源：http://www.thelancet.com/infection/財團法人台灣紅絲帶基金會編譯

    人畜共通疾病與氣候變化、生態系統變化和人類健康息息相關。人畜共通疾病或人畜共患病(Zoonotic diseases, or zoonoses) 通常被定義為在脊椎動物和人類之間自然傳播的疾病和感染症。 這篇社論廣泛地提到了人畜共通病，除包括它的經典定義，也包括起源於動物的病原體，這些病原體後來適應了無論在有或沒有媒介的人與人之間傳播。由於森林砍伐和生態系統的變化，例如土地遷移、棲息地改變、全球變暖以及病原體和載體生物學特性的變化，伊波拉病毒病等野生動物溢出引起的人畜共通病以驚人的速度出現，例如生存、毒力和繁殖。生態系統破壞導致的生物多樣性下降加劇了人畜共通病的傳播。生活在低收入和中等收入國家 (LMIC) 的人們的健康將受到不成比例的影響，因為他們的醫療保健系統脆弱，資源匱乏，地方性傳染病負擔沉重。

    根據 2022 年 10 月 25 日出版的關於《刺胳針人類健康和氣候變化的倒數計時》年度刊物，《巴黎協定》確定的 1·5˚C 門檻將在 5 年內被超過的可能性為 48%。這將影響所有形式的人畜共通病，無論是水、食物、媒介、囓齒動物還是空氣傳播的來源，還將增加具有大流行潛力的新型感染症的出現。

    登革熱和瘧疾等病媒傳播疾病的氣候適應性正在發生變化，1951-60 年至 2012-2021 年間登革熱的傳播增加了 12% 就證明了這一點，而瘧疾有可能在全球範圍內再次出現 南歐由於地理範圍擴大。氣候變化將對利甚曼病產生影響，因為它的分佈由於地理範圍的擴大而發生變化（例如，在巴西，預計到 21 世紀末每年利甚曼病住院人數將增長 15%）。 由於氣候變化，預計未來 20-50 年東非的血吸蟲感染風險將增加 20%。

面對這種嚴峻的局面，還有希望的曙光，例如個人對減緩氣候變化的承諾增加，媒體報導增加，以及決策者在高層會議上的參與。此類會議之一是 2022 年 11 月 6 日至 18 日在埃及沙姆.沙伊赫舉行的聯合國氣候變化締約方大會 (COP)。一項歷史性的氣候正義協議已達成通過損失和損害基金，其中高收入國家和最大的二氧化碳排放國將向巴基斯坦和馬爾地夫等儘管本身是低排放國但已成為氣候變化受害者的國家提供支持。該基金將如何運作的細節還有很多不足之處；目前尚不清楚什麼門檻將觸發支出、哪些國家將捐款以及捐款是否足夠。在對 1·5°C 目標的承諾方面，美國、其他高收入國家和中國之間存在明顯差異，而中國對這一目標的關注度明顯較低。由於沙烏地阿拉伯等石油資源豐富的國家反對，COP27 的最終文本改為「低排放和可再生能源」，因此逐步淘汰化石燃料也沒有實現 這些要點強調，破壞將繼續發生，氣候變化和人畜共通病的受害者將別無選擇，只能不斷尋求幫助來解決這些問題，而這往往是不夠的。

    世界正處於一個轉折點，將我們星球的健康置於其努力的中心將確保地球上的生命得到保護。我們必須阻止潛在的氣候變化，同時採取其他行動來減輕人畜共通病風險。未來，生態知識將成為指導短期和長期衛生政策決策的焦點。可以提前數週或數月告知我們特定人畜共通病危害的模型對於支持及時的預防策略和健康規劃至關重要。短期內，在氣候變化加劇的地區開展疾病監測對於有效應對新型和新出現的人畜共通病至關重要。 諸如 健康一體 (One Health) 之類的綜合框架是在面對氣候變化時建立可持續和有抵抗力的衛生系統的前進方向。科學家可以發揮巨大作用，因為他們的研究工作可以指導政策制定者協助中低收入國家，不僅是建立降低風險的能力和促進醫療保健，還可以補充和創新可用的藥物、疫苗和技術。政策制定者和個人必須立即採取行動，幫助防止另一場大流行病的威脅。 ■ 剌胳針傳染病

Twin threats: climate change and zoonoses

http://www.thelancet.com/infection

  Zoonotic diseases are at the nexus of climate change, changes in ecosystems, and human health. Zoonotic diseases, or zoonoses, are classically defined as diseases and infections that are naturally transmitted between vertebrate animals and humans. This editorial refers to zoonoses in a broad way and includes both the classical definition of it, and to pathogens that originated in animals that subsequently adapted to transmit between humans with or without vectors. Zoonoses derived from spillover from wildlife, such as Ebola virus disease have been emerging at an alarming rate due to deforestation and the change in ecosystems, such as land shifts, habitat alterations, global warming, and changes in the biological characteristics of pathogens and vectors, such as survival, virulence, and reproduction. Biodiversity decline from ecosystem destruction increases zoonotic spread. The health of people living in low-income and middle-income countries (LMICs) will be disproportionately affected as they have vulnerable health-care systems with scant resources and a high burden of endemic infectious diseases. 

  According to the annual publication of The Lancet Countdown on human health and climate change published on Oct 25, 2022, there is a 48% chance that the 1·5˚C threshold decided in the Paris Agreement will be exceeded within 5 years. This will impact on all forms of zoonoses be it water, food, vector, rodent, or airborne origin and will also increase the emergence of novel infections with pandemic potential. 

  The climate suitability for vector-borne diseases, such as dengue and malaria, is changing, as witnessed by a 12% increase in dengue’s transmission between 1951–60 and 2012–2021, and in the case of malaria with a possibility of it reappearing in southern Europe due to increased geographical range. Climate change will have an impact on leishmaniasis as its distribution is changing due to increased geographical range (eg, in Brazil a 15% growth in annual leishmaniasis hospital admissions is forecast by the end of the 21st century). Schistosoma infection risk in east Africa is predicted to increase by 20% over the next 20–50 years due to climate change. 

  In the face of this grim picture, there are rays of hope, such as the increased individual commitment to mitigate climate change, increased media coverage, and the engagement of policy makers at high level meetings. One such meeting is the UN Climate Change Conference of the Parties (COP) which took place in Sharm El-Sheikh, Egypt, Nov 6–18, 2022. A historic deal has been reached on climate justice with the loss and damage fund in which high income countries and the largest CO2 emitters will provide support to those countries that have been victims of climate change despite being low emitters themselves, such as Pakistan and the Maldives. The details of how this fund will operate leaves much to be desired; there was no clarity as to what threshold will trigger a payout, which countries will contribute, and whether contributions will be enough. Stark disparity was observed between the USA, other high-income countries, and China in terms of commitment towards the 1·5°C target, with China notably less concerned about this goal. Phasing out of fossil fuels was also not achieved with the final text of COP27 being changed to “low emission and renewable energy” due to opposition by oil-rich nations, such as Saudi Arabia. These points underscore that damage will continue to occur and victims of climate change and zoonoses will be left with no option except continually seeking help to deal with these issues, which will often not be sufficient. 

  The world is at a tipping point at which putting the health of our planet at the centre of its efforts will ensure life on Earth is preserved. We must stop the underlying climate change and, in the meantime, take other actions to mitigate zoonotic risk. For the future, ecological knowledge will be a focal point in guiding both shortterm and long-term health policy decisions. Models that can inform us of specific zoonotic hazards weeks or months in advance will be pivotal for supporting timely prevention strategies and health planning. In the short term, disease surveillance in areas with increased climate change will be crucial for launching an effective response to novel and emerging zoonoses. Integrated frameworks, such as One Health, are the way forward for building sustainable and resistant health systems in the face of climate change. Scientists have a huge part to play as their research efforts can guide policy makers to assist LMICs, not just in building capacity to lower risk and promoting health care, but by replenishing and innovating the available drugs, vaccines, and technologies. Policy makers and individuals have to act now to help prevent the threat of another pandemic. ■ The Lancet Infectious Diseases