大流行病:歷史與預防| NutritionFacts.org

17 5 月, 2020


聯合國認為,人類面臨的兩個最大威脅是氣候變化和新出現的傳染病,尤其是大流行性流感。可以理解的大流行討論和辯論的當前焦點集中在我們在公共衛生界中所說的二級預防:調解下一次大流行的影響,這是一種類似於乳腺X線攝影的干預措施。乳房X線照片無法預防癌症,但是例如,如果足夠早發現,我們也許可以降低發病率和死亡率。而且,與大流行性計劃相同。但是,首要的預防是什麼,首先是預防大流行病毒出現的可能性?像癌症一樣,根本原因可能是多因素的,難以弄清,但儘管如此,這個問題仍然值得探討,而我今天想在這裡解決。

讓我們回頭幾年。 1981年。羅納德·裡根(Ronald Reagan)在美國宣誓就職。 MTV開始播放印第安納·瓊斯(Indiana Jones),而吃豆子的狂熱風靡一時。 6月,CDC發布了一個小公告。看來,洛杉磯有五名男子死於一種奇怪的症狀。從最初開始,艾滋病就已經殺死了2500萬人。現在,濫交,血液儲備,靜脈注射毒品的使用促進了艾滋病病毒的傳播。但是該病毒最初是從哪裡來的?當然,艾滋病不是我們唯一的新疾病。那裡有非典,埃博拉病毒,瘋牛病,禽流感……但是新興疾病從何而來?好吧,讓我們再回頭一點。人類已經在地球上生活了數百萬年,但在人類的大多數進化過程中,都沒有流行病。

從來沒有人得過麻疹,因為不存在麻疹。直到大約一萬年前,沒有人得了天花,沒有人得了流感,甚至沒有感冒。自人類進化以來,醫學人類學家已經確定了疾病的三個主要時期,第一階段始於10,000年前的動物馴化。當我們將動物帶入the場時,它們帶來了疾病。例如,當我們馴化牛和羊時,我們還馴化了牛瘟病毒,牛瘟病毒變成了人類麻疹,現在被認為是一種相對良性的疾病。在過去的150年中,麻疹已殺死2億人。從某種意義上說,所有這些死亡最終都可以追溯到數百年以來的第一批牛的馴服。天花可能來自駱駝痘。我們馴養了豬,並百日咳。我們馴養了雞,得到了傷寒和傷寒瑪麗,馴養了鴨子,並得了流感。在養鴨之前,可能沒有人感染過流感。麻風病可能來自水牛,普通感冒來自馬。野馬多久一次有機會打噴嚏到人類的集體面孔,直到被打斷和綁住?在那之前,普通感冒只對他們而言是普通的。

在他的普利策獎獲獎書中, 槍支,細菌和鋼鐵,戴蒙德(Diamond)教授試圖解釋為何登陸歐洲人的疾病消滅了95%的美洲原住民,而不是相反。為什麼美洲原住民瘟疫沒有殺死歐洲人?好吧,因為沒有瘟疫。在他的“牲畜的致命禮物”一章中,他解釋了在歐洲人到來之前,我們如何擁有水牛,但沒有馴化的水牛。所以,沒有麻疹。在更新世的冰河時代,美洲駝被消滅了。所以,沒有天花。沒有豬,所以沒有百日咳。沒有雞,所以沒有傷寒。因此,儘管人們在歐洲和亞洲數以百萬計的殺戮性災難中喪生,但在所謂的新世界中,沒有人死於疾病,因為基本上沒有外國動物可以馴養。沒有動物疾病的溢出。

人類疾病的下一個偉大時期始於幾百年前的18和19世紀工業革命,導致所謂的文明疾病流行:糖尿病,肥胖,心髒病,癌症等。但是到20世紀中葉,至少傳染病時代已經結束。我們吃了青黴素,克服了小兒麻痺症,消滅了天花。實際上,1968年,美國外科醫生宣布抗擊傳染病的戰爭已經勝利。 1975年,耶魯大學醫學院院長宣布,除了肺癌以外,沒有發現其他新疾病。但是,即使是諾貝爾獎獲得者也被當時的樂觀情緒所吸引。一位著名病毒學家在1962年的一本教科書中寫道:“寫傳染病幾乎就是寫一些已被傳給歷史的東西。他寫道,對傳染病未來的最可能的預測是,它將非常無聊。

但是後來,情況發生了變化。在美國數十年來傳染病死亡率下降之後,近幾十年來這種趨勢已經逆轉。這是過去50年左右的CDC隨時間變化的傳染病死亡率的圖表。如您所見,它開始下降。下降,下降,下降,但是在1975年左右,它開始回升。死於傳染病的美國人人數開始回升。從1975年左右開始,新疾病開始出現並以醫學史上聞所未聞的速度重新出現。 30年內出現了30多種新疾病,其中大部分是新發現的病毒。實際上,新興傳染病的整個概念已經不僅僅出於醫學領域的好奇。現在,這是一門完整的學科,真的成為了中心舞台。

根據美國醫學研究所的說法,我們可能很快就會面臨所謂的微生物威脅災難性風暴。我們現在正處於人類疾病的第三個時代,似乎只是在30年前才開始。醫學史學家稱這次是我們度過新瘟疫時代的時代,幾乎所有疾病都來自動物。

但是我們在一萬年前就馴養了動物。最近幾十年來發生了什麼變化,使我們進入了目前的局勢?好吧,我們正在改變動物的生活方式。以康涅狄格州為例,在1975年,萊姆病首次被發現。自成立以來,它遍及所有50個州,影響了大約100,000名美國人。萊姆病是由細菌感染的鹿tick引起的,但主要宿主實際上不是鹿,而是白腳老鼠。壁蝨本身並不是真的很可愛,但是我們一直在與這些傢伙永遠分享樹林。最近發生的變化是郊區。黑腳tick生活在白腳老鼠上,被林地掠食者拒之門外。但是後來,開發人員進來,將美國的林地砍成碎片,嚇跑了狐狸和山貓,現在我們有了更多的老鼠,更多的壁蝨和更多的疾病。

我們正在改變動物的生活方式。往回走一點,第二次世界大戰期間與大型養牛國作戰。阿根廷所做的就是利用這種狀況,以犧牲雨林為代價,大大擴展了牛肉行業。在那兒,我們發現了致命的人類病毒,或者更確切地說,它發現了我們,雨林的所謂漢堡包化後來暴露了整個非洲的出血熱病毒。轉向世界的另一端,在砍伐非洲的雨林中,還暴露了許多其他出血熱病毒,包括拉沙病毒,裂谷熱,當然還有埃博拉病毒。現在,入侵非洲雨林的伐木之路被跨國木材公司砍伐而深深侵入雨林,拖著飢餓的農民工,他們靠叢林肉生存:為食物而殺死的野生動物。現在,這包括超過26種不同的靈長類動物,包括一些瀕臨滅絕的大猿種,大猩猩,黑猩猩,這些人被槍殺,屠宰,熏制和出售為食品。現在,通過吞噬我們的靈長類動物,我們可能會暴露於特別根據自身靈長類動物生理特性進行微調的病毒。實際上,例如,最近的埃博拉疫情可追溯到暴露於被捕食的被感染大猩猩的屍體。現在,與像HIV這樣的病毒相比,埃博拉病毒是我們最致命的感染之一,但傳播效率卻不高。

關於艾滋病病毒出現的主要理論是由於狩獵,屠宰和食用受污染的叢林肉而直接暴露於動物血液和分泌物中。專家認為,最有可能的情況是,艾滋病病毒是由人類鋸齒進入叢林,沿途屠殺黑猩猩的肉而引起的。現在在非洲許多國家,艾滋病毒的流行率已超過成年人口的25%,數百萬孤兒因此而來。幾十年前有人屠殺了黑猩猩,現在有2500萬人死亡。但是野生生物已經被獵殺了數千年。是的,但是從來沒有像現在這樣。

隨著野生動物肉的需求超過當地供應,各國已經建立了這些集約化飼養場,將野生動物擠在狹窄的骯髒籠子裡,然後走私到世界各地。這種密集的商業性叢林肉貿易實際上始於亞洲的活躍市場,特別是廣東省(香港周邊的南部省份),由此引發了目前的禽流感威脅。果子狸,在這些中國動物市場中很受歡迎的商品。除了因果肉而飼養外,他們還生產世界上最昂貴的咖啡。所謂的狐狸糞便咖啡是通過將咖啡豆餵入圈養的麝香貓而製成的,然後(您猜對了)從糞便中回收部分消化的咖啡豆。據說,肛門腺分泌的麝香狀黃油稠稠物質使這種咖啡具有獨特的風味。也許有人會說這種獨特的飲料對最後一滴是有益的。對不起。該動物被認為是SARS流行的罪魁禍首。引用醫學雜誌, 柳葉刀,“華南地區的美食選擇。” “華南地區的烹飪選擇導致了香港的致命感染。”

隨後,發生8000例SARS。在六大洲的30個國家中,近一千人死亡。也許他們應該只是堅持使用星巴克。這些活的動物市場帶有一類病毒,在人類醫學中,我們只是以引起普通感冒而聞名,似乎使它們成為殺手,SARS,然後在世界範圍內傳播。病毒可以逃脫雨林中的動物,無論它們是活的還是死的,都是寵物或肉。 2003年,異國寵物貿易將猴痘從西非叢林帶到了威斯康星州。實際上,鳥類走私實際上是將西尼羅河病毒帶入西半球的原因。在這裡,它於99年登陸紐約,並在全國范圍內傳播。數以百計的人死亡,可能都是由於一隻進口寵物鳥造成的。

因此,我們正在改變動物的生活方式,為這些新疾病的出現做出了貢獻。但是,您知道,我們改變與動物的關係的一種方式確實使所有其他動物都黯然失色。為了應對這種大量湧現的和重新出現的傳染病,世界三個主要當局聚集在一起進行聯合磋商。世界衛生組織,聯合國糧食及農業組織和世界動物衛生組織(世界領先的獸醫當局)聚集在一起,探索了這一時代新生鼠疫的關鍵根源。他們提出了四個,四個主要風險-這些新疾病的出現和傳播的四個主要風險因素主題。是的,他們談論了異國寵物貿易。他們談論叢林肉,但名單上排名第一的是全世界對動物蛋白的需求不斷增長。是的,我們在一萬年前就馴化了動物,但從未像現在這樣馴化過動物,尤其是豬和家禽。

雞過去常常在the附近啄食,但是現在飼養的肉類雞通常被存放在容納成千上萬隻鳥的棚屋中。現在,這個星球上大約有一半的產蛋母雞被關在所謂的電池籠中。這些小的貧瘠的金屬外殼沿著長排和無窗棚延伸。一個農場最多可以飼養一百萬隻雞。現在,地球上約有一半的豬再次被擠入了密集的禁閉行動。您知道,舊的麥克唐納農場已被新的麥克唐納農場取代。這些密集的系統代表了10,000年以來人類與動物關係的最深刻變化。而且,毫不奇怪,它們是疾病的溫床。

一些快照。中國,最大的豬肉生產國,2005年,前所未有地爆發了一種新興的豬病原體,即豬鏈球菌,在處理受感染豬肉產品的人們中引起腦膜炎和耳聾。數百人受到感染,是有史以來最致命的毒株。為什麼?嗯,根據世界衛生組織的說法,確實確實是這些密集的隔離條件。美國農業部詳細說明:“所有鏈球菌開始都是無害的天然腸道菌群,但隨後由於過度擁擠,通風不足而導致的壓力免疫抑製作用會導致蟲子侵入,引起腦,血液,肺,心臟,和死亡。”開始無害,變成致命。這些條件似乎可以做到。可以說,這不是動物本應如何生活的方式。

馬來西亞的養豬場出生了Nipah病毒,這是人類最致命的感染之一:一種傳染性呼吸道疾病殺死了40%的感染者,造成了復發和腦部感染,並將其推入美國的官方生物恐怖主義劑名單。再次,據該領域的一位領導人稱,這似乎是我們現在飼養這些動物的方式。因此,人類疾病的三個時代的特徵可能首先是馴化疾病,然後是工業化疾病,最後是土地利用和農業集約化疾病。我們以牛,羊等天然草食動物為食,通過給他們屠宰場的糞便,血液和糞便餵食,將它們變成食肉動物和食人動物,然後我們取下了病得無法行走的動物,將它們餵給人,現在我們有了瘋牛疾病。我們通過卡車為農場動物餵食抗生素。

這是每年用於所有人類醫學的抗菌素總量。現在,對比一下我們在如此壓力大,不衛生的環境中餵給農場動物的飼料,只是為了促進生長或預防疾病。每年數百萬英鎊,現在我們有了這些具有多重耐藥性的細菌,而且作為醫生,我們已經沒有足夠的抗生素選擇了。紐約大學的科學家追踪了其中一些“超級臭蟲”的踪跡,例如從向雞大量飼餵Cipro類抗生素開始,然後我們–屠宰時is體受到糞便污染。我們在超市購買被糞便污染的雞肉,導致人類感染時間更長或更嚴重。

CDC最近真的束手無策了。他們在三年內花費了一百萬美元,對剛入院的患者進行了直腸拭子檢查。這就是他們發現的。從本質上講,他們發現與新鮮或冷凍家禽零接觸的那些體內的這些抗生素抗性細菌的零生長。但是,至少這些所謂的超級錯誤無法有效地從一個人傳播到另一個人。工業動物農業似乎傾向於生產這些新型致死性人類病原體,如果這些動物工廠產生了能夠引起全球疾病大流行的病毒,該怎麼辦?

讓我透視這些新的動物疾病威脅。 SARS感染了數千人,造成數百人死亡。尼法感染了數百人,殺死了數十人。豬鏈球菌感染分數,殺死數十人。現在,艾滋病已經感染了數百萬人,但地球上只有一種病毒可以迅速感染數十億,這就是流感。流感是所謂的人類最後一場大瘟疫,是近來唯一能夠真正造成全球災難的已知病原體。與許多其他重要疾病(如瘧疾,主要局限於赤道)或像HIV(僅通過液體傳播)之類的病毒不同,流感病毒被認為是唯一能夠在數月內真正感染一半人類的病原體。

自從鳥類首次馴化以來,在我們作為物種的4,500多年中,流感一直是我們已知的最具傳染性的疾病之一。但是,直到這種高致病性,高致病性菌株H5N1出現以來,流感病毒才成為我們最致命的病毒之一。 H5N1病毒在2004年,2005年,2006年擴散到亞洲,並一直延續到今天,僅殺死了一百,數百人。而且並非最小化,每一次死亡都是一場可怕的悲劇。但是,在這個世界上繼續有數百萬人死於艾滋病,結核病等疾病的世界中,為什麼人們對所謂的禽流感如此擔憂?因為以前發生過由於上一次禽流感病毒適應人類,因此引發了人類歷史上最嚴重的瘟疫:1918年的流感大流行。

現代流感病毒株往往使年輕健康的成年人倖免於難,但1918年的病毒卻在人們的成年時期殺死了人們。 1918年,四分之一的美國人患了病。這是“人口死亡百分比”的圖表。人類最偉大的大規模殺人犯躲藏了近一個世紀,直到在阿拉斯加發掘出一個集體墳墓。大流行的受害者在多年凍土中凍結了80年,在她的肺部留下了病毒痕跡,這使得科學家們可以逐字母地拼湊1918年病毒的遺傳密碼,從而解決了有史以來最偉大的醫學偵探故事。

人類最大的殺手是禽流感。具有諷刺意味的是,1918年9月11日是美國的首例平民傷亡,然後在一個月內,這是第一周,第二週,第三週,第四周。現在是1918年。我們在這裡談論蒸汽機車。倫敦帝國理工學院的科學家進行了模擬,以了解當今流行病如何在英國傳播。洛斯阿拉莫斯(Los Alamos)的科學家通過他們的超級計算機進行了仿真,以了解大流行在商業航空旅行的一天中如何傳播。在此,它在此模擬中達到了洛杉磯,並在數週內覆蓋了整個國家。 1918年,有50至1億人喪生。今天,類似的病毒可以殺死更多更多的病毒。隨著數百萬甚至數小時甚至數小時的肌肉疼痛和發燒的結束,數百萬人開始從眼睛,鼻孔,耳朵到肺部出血。無家可歸的孤兒,其父母去世,在空蕩蕩的街道上徘徊。飽受折磨的東方的一位受苦的官員向西方發出了緊急警告。 “請僱用您的木工,讓他們製作棺材,然後僱用您的街頭工人,將他們安置在挖墓地上。”

這是一個剪輯 紐約時報。當時,瘟疫的受害者到處都是,火焰吞噬了巨大的屍體。許多受害者被自己的血淋淋的水勒死。他們的屍體因窒息而呈淡藍色,據說在太平間外面像臍帶木一樣堆放,城市的棺材用盡了,所以他們挖了墳墓。這種源於禽流感的病毒在25週內殺死的人數比艾滋病在25年內殺死的人數還要多。在1918年的大流行中,沒有戰爭,沒有瘟疫,沒有飢荒在如此短的時間內殺死瞭如此多的人。

然而在1918年,該病的死亡率不到5%。此處的估計值是基於同一2%至3%的死亡率,在下一次大流行中可能有數千萬人死亡。美國疾病預防控制中心現在將其稱為第5類大流行,死亡率約為2%,約有200萬美國人死亡。這就是2%。目前,H5N1正式殺死了一半以上的人類受害者。似乎還沒有人為這種疾病而生。世界領先的禽流感權威羅伯特·韋伯斯特(Robert Webster)博士說:“如果追溯到1918年,將有2.5%的人死亡。有多少人死於禽流感? 50%。自瘟疫爆發以來,我們從未見過這樣的事件。”

每年有多達6000萬美國人得流感。如果突然變成致命的怎麼辦?這就是讓每個人都無法入睡的原因:像H5N1這樣的病毒可能會引發人間大流行,無論多麼微小。這就像將最具有傳染性的已知疾病之一流感與最致命的疾病之一結合起來一樣,例如將埃博拉等疾病與普通感冒相結合。

這種病毒是從哪裡來的?好吧,當前圍繞禽流感的對話談到了潛在的H5N1大流行,就好像是自然災害(颶風,地震),我們無法控制。但是,現實是,下一次大流行可能更多是我們自己造成的非自然災難。在禽類中,禽流感已從一種極為罕見的疾病變為現在每年流行的一種。在本世紀頭幾年,高致病性禽流感的暴發數量已經超過了整個20世紀記錄的暴發總數。您會注意到,這是五年間隔。好吧,在2006年的前五個月中,我們已經到了這裡,沒有中斷,一直持續到今天。如果看一看所涉及的鳥類數量,其升級會更加劇烈。以這樣的規模,直到1980年代甚至還沒有出現過。禽流感似乎正在迅速發展。正如一位領先的流感專家對科學所說的那樣,“我們已經從幾片雪花變成了雪崩。”雞肉暴發的增加與向人類的傳播增加密切相關。

大約10年前,基本上沒有人知道,沒有一個人直接從禽流感中生病,但是自從H5N1於1997年出現以來,其他四種雞流感病毒已經感染了從香港到紐約市的人。去年,我們可以為英格蘭和威爾士的四個案件添加另一個粉紅色的戒指。在荷蘭的爆發中,政府進行的一項調查顯示,有證據表明有1000人感染了這種病毒,有症狀的家禽工人將病毒傳播給了高達59%的家庭成員。人與人之間的傳播受季節性流感的影響。因此,十年前或十二年前,基本上沒有人感染禽流感,現在全球各大洲已有1000多例。現在荷蘭爆發了疫情,有3000萬隻雞死亡,但只有一人死亡;其中一名主治獸醫不幸死亡,因此荷蘭病毒擅長傳播,但不能殺死人。

H5N1是相反的,對嗎? H5N1甚至不擅長從鳥類傳播到人。看,已經有10年了,超過10年了。只有少數幾百人被感染。而目前-肯定不擅長在人與人之間傳播。但是,這種病毒對人類的致命性是致命的:比有史以來最嚴重的流感病毒(造成1918年大流行)的致死率高10倍以上。因此,荷蘭爆發給我們顯示的是,這種病毒可以進化為直接在人與人之間傳播。 H5N1向我們展示的是,該病毒可以演變為有效的人類殺手。如果允許這種趨勢繼續下去,我們的噩夢可能有一天會實現。兩全其美,極具感染力和致命性。因此,要減緩或阻止最近這種高致病性流感病毒的迅速出現,必須首先問好,到底是什麼引發了雪崩?最近幾十年來發生了什麼變化,才能將這一切帶給我們?

H5N1的出現被歸咎於自由放養的雞群和野鳥。但是人們在後院飼養雞已有數千年的歷史了,鳥類已經遷徙了數百萬。禽流感已經永遠存在。是什麼使禽流感成為殺手?好吧,《與吉姆·勒勒的新聞時報》的高級通訊員把這個問題交給了所謂的流感研究教父韋伯斯特博士。 “在過去的十年中,在質上是否有所不同,是否使這種疾病有可能做以前從未做過的事情?某種不斷變化的條件突然點燃了火柴的火柴?”韋伯斯特回答。他說:“耕作方式已經改變。”他談到要在農場長大,但是“現在我們將數百萬隻雞放進了養豬場隔壁的養雞場。而且這種病毒有機會進入這些雞肉工廠之一,並不斷產生數十億個這樣的突變。因此,我們所改變的是飼養動物的方式以及與這些動物的互動。”然後,他談到病毒是如何從工廠逸出並感染野禽的。他說那就是改變了。我們已經改變了飼養動物的方式。但是,我們改變了以數十億美元飼養動物的方式。

我們每天屠宰的雞的數量,從一翼到另一翼,將包裹世界赤道的兩倍以上。禽流感生態的重大轉變是全球家禽業的集約化。發展中國家的肉和蛋消費量激增,導致了這些具有工業規模的商業雞設施,可以說是這些所謂“超級流感”的出現和傳播的理想風暴環境。在1980年代初期,中國幾乎所有的雞都是在小型的後院室外雞群中飼養的,但是現在中國有63,000個CAFOS(集中動物飼養業務),其中一些所謂的工廠化農場僅將一千萬隻禽鳥飼養在一處。農場。世界衛生組織指責H5N1,SARS,Nipah病毒以及所有這些致命的新出現的亞洲病毒的出現,部分歸因於他們所說的這種密集動物農業中動物產品的過度消費。

聯合國糧食及農業組織開始說:“近年來,人類流感問題似乎正在加速發展。”這就是他們的意思。這是來自世界衛生組織的。這些都是上個世紀左右感染人類的所有新型流感病毒。現在,將注意力轉向1995年。似乎也像雪崩一樣撲向人們。但為什麼?嗯,據世界領先的農業主管部門預計,這在很大程度上與家禽生產的集約化有關,也可能與養豬業的集約化有關。他們在糧農組織內部文件中詳細闡述了“雞到雞的傳播,特別是在這種集約化飼養條件的輔助下,會導致病毒轉移,適應更嚴重的高致病性感染。集約化生產有利於病毒在所謂的“感染”中從低致病性到高致病性類型的迅速傳播。”

看來,工廠農場可以看作是這種病毒高度致病性菌株出現的孵化器。在此圖中,他們實際上追踪了人類大流行的路徑,首先是對家禽產品的需求增加,最後是一種能夠在人與人之間傳播的病毒。實際上,聯合國已經呼籲所有政府發揮所謂的工廠化農業的作用。聯合國新聞稿引述:“政府,地方當局,國際機構需要在打擊工廠化農業方面發揮更大的作用,這些活動與這些活禽市場相結合,為病毒傳播和突變成更多的理想條件。危險形式。”

讓我告訴你它是如何工作的。所有禽流感病毒一開始對鳥類和人類無害。了解非常重要。他們開始無害。禽流感作為水禽(如鴨子)的無害腸道病毒和水傳播病毒已經存在了數百萬年。我說,嗯,鴨子的腸蟲怎麼會在人的咳嗽中結束?好吧,在人中,病毒必須使我們生病才能傳播,必須使我們咳嗽才能將病毒從一個人傳播到另一個人。有了這種病毒的天然儲存庫,如鴨子之類的水禽,該病毒就不必讓鴨子生病即可傳播。實際上,不讓鴨子生病是病毒進化的最大利益,因為死鴨不會飛得很遠。所以。病毒悄無聲息地繁殖,鴨子的腸壁被分泌到池塘水中,被另一隻鴨子吞下,這種循環持續了數百年之久,沒有人受到傷害。但是,如果將被感染的鴨子拖到活禽市場,例如擠在足夠高的籠子裡,以便在陸生鳥類,陸生鳥類(如雞)上發現受病毒感染的糞便,那麼,該病毒就會出現問題。如果病毒在雞的腸道中發現,它就不再具有易於通過水傳播的奢侈品。雞不在池塘里嬉戲,所以病毒必須突變或死亡。

對於我們來說不幸的是,變異似乎是流感病毒最擅長的。因此,在其天然水庫中,它被描述為處於完全進化停滯狀態,無害,但是當被扔進陸基鳥類之類的新宿主中時,它會迅速開始突變,並獲得適應新宿主的突變。例如,在露天環境中,它必須抵抗脫水,並且可能必須擴散到不同的器官以尋找新的旅行方式。腸道將不再起作用,它們可能會發現肺部並成為空氣傳播的病原體,這對陸地哺乳動物(如我們自己)來說是個壞消息。以水生病毒的形式進入雞,但可能以流感的形式出現。在其新宿主中,這種病毒變得越強毒,就越具有暴力性,它可能越快地使其新宿主的免疫系統不堪重負。但是,如果病毒變得太致命,它可能不會傳播到很遠。至少在室外環境中,如果病毒殺死宿主的速度過快,則該動物可能已經死了,然後才有機會傳播給太多其他動物。因此,在自然界中,這些病毒的毒性有一個自然的限制-或至少到現在為止。

進入集約化家禽生產。當下一個喙距離只有幾英寸(幾英寸)時,這些病毒的獲取方式可能就沒有限制了。進化生物學家認為,這是出現像H5N1這樣的高毒捕食型病毒的關鍵。固定宿主的疾病傳播。 See, when you have a situation where the healthy cannot escape the disease, where the virus can knock you flat, and still transmit just because you’re so crowded, then there may be no stopping rapidly-mutating viruses from becoming truly ferocious. And this may explain the virus of 1918, rising out of the trenches of World War I. There were these crowded troop transports; boxcars were labeled “8 horses or 40 men.” So, when this harmless virus found itself in these kind of conditions, it turned deadly. Millions forced together under cramped quarters; no escaping a sick comrade. This is thought to be where the virus of 1918 gained its virulence.

From the virus’s point of view though, these same trench warfare conditions exist today. In every industrial chicken shed, every industrial egg operation, confined, crowded, stressed, but by the billions, not just millions. The industry is slowly waking up to this growing realization that viruses previously innocuous to natural host species have in all probability become more virulent by passes through these large commercial populations.

This from an industry journal. Starts out harmless, turns deadly. That’s what these conditions may be able to do. This is not arguably how animals were meant to live. So how does the poultry industry feel about the possibility that its own animal factories may produce a virus capable of killing millions of people around the world? Well, the executive editor of “Poultry” magazine wrote an editorial on just that topic. She wrote, “The prospect of a virulent flu, to which we have absolutely no resistance is frightening. However, to me, the threat is much greater to the poultry industry. I’m not as worried about the U.S human population dying from bird flu as I am that there will be no chicken to eat.” This is this is how the Department of Interior puts it. “Domesticated poultry is the necessary stepping stone to create a pandemic strain of influenza.” Now we used to think pigs were an important link in this chain, so this—probably not a good idea. H5N1 found a way, it seems, not only to kill people directly, but seems to have gone full circle, reinfecting its natural hosts––migratory aquatic species––who could potentially fly this factory farm virus to continents around the world.

Now, unfortunately for us, there’s some quirk of evolution. The respiratory tract of a chicken seems to bear striking resemblance to our own primate respiratory tract on a molecular level, on a virus receptor level. So as the virus gets better at infecting, killing chickens, the virus may be getting better at infecting and killing us. Virologist Earl Brown, specialist in the evolution of influenza viruses. “You have to say,” Dr. Brown concluded, “again, this high-intensity chicken rearing, really the perfect environment for the evolution for generating virulent avian flu virus.”

Now in contrast, there has never been a single recorded emergence of a highly pathogenic flu virus ever from an outdoor chicken flock. Never once has a dangerous deadly virus ever arisen that we know of in chickens kept outside. You can breed a deadly virus here. It can escape. In fact, backyard birds, free-ranging flocks, even wild birds, but that transition from harmless to deadly always seems to happen in these kind of conditions, because of the overcrowding. Remember, transmission from immobilized hosts, because of the sheer numbers. Because of the inadequate ventilation, the dankness helps keep the virus alive. Because of the stress crippling their immune systems. Because of the filth. The virus is in the feces that they’re lying in, which, decomposing, releasing ammonia, burning their respiratory tracts, predisposing them to respiratory infection in the first place. And because there may be no sunlight. The UV rays and sunlight are actually quite effective in destroying the influenza virus. 30 minutes of direct sunlight completely inactivates H5N1, but it can last for days in the shade, and weeks in moist manure.

So, you put all these factors together, and what you have is this kind of perfect storm environment for the emergence and spread of new super strains of influenza. But what about biosecurity? Don’t we want all the birds confined indoors, away from waterfowl? I mean, does it matter? If these kind of conditions can turn a harmless virus into a deadly virus, if the harmless virus can’t get inside in the first place? Well, an FAO research report addressed this very question. They, in their evidence-based analysis, they looked at the best data set available: a massive survey of flocks in Thailand, in which over a million birds were tested for H5N1, in factory farms and backyard flocks. And what they expected to find was that backyard flocks would be at higher risk for infection, because they’re just out there in the open. What they found was exactly the opposite. They found that backyard flocks are at significantly lower risk of infection, compared to commercial scale operations. Industrial quail and chicken operations were at least four times more likely to become infected than backyard flocks. So, not only may factory farms be the incubators for the original emergence of high-path strains, based on the best science available, they may also play a role in the spread, the subsequent spread of the virus as well––in part because of the massive inputs and outputs required for this industrial style of animal agriculture. Tons of feed and water go in. Tons of waste comes out. Tens of thousands of flies buzzing around. And, these high-volume ventilation fans blowing dust and waste out into the countryside, potentially contaminating the air, the soil, insects, rodents, transport. Industrial-style production can lead to industrial-style contamination of the environment.

Researchers at Johns Hopkins University School of Public Health looked back and realized that their conclusions were actually consistent with other high path outbreaks, whether in the Netherlands, Canada, Italy, other diseases. Factory farms consistently at higher risk. They concluded that there’s no empirical evidence to support this myth that backyard flocks are somehow the crux of the problem. And again, people have been raising birds in their backyards for about 4,000 years before this disease erupted out of control. On other factors, the studies have uncovered widespread disregard for biosecurity, even in developed countries. which claim to have the best biosecurity in the world. According to North Carolina University Poultry Health Management, high biosecurity is still wishful thinking in many areas of intensive poultry production.

A bird flu outbreak in Virginia in 2002 led to the deaths of four million birds. Found its way inside 200 factory farms, highlighting just how wishful the thinking is that industrial poultry populations are somehow completely protected against this kind of infection. Based on the rapid spread of avian influenza in Virginia recently, this decade, USDA poultry virologists conclude the obvious, that biosecurity on many farms is simply inadequate. Investigators from the University of Maryland surveyed chicken facilities throughout the Delaware, Maryland, and Virginia peninsula, perhaps the most concentrated density of chickens in the world, and concluded that U.S. chicken flocks, were constantly at risk for infection, triggered by these poor biosecurity practices. But even if the industry had perfect compliance with these guidelines, even if everyone going in and out stepped in antiseptic foot baths, scrubbed their boots, washed their hands, even with perfect compliance, it likely would not be enough.

We now know that H5N1 can be carried by flies. You cannot keep flies out of a poultry shed. See, H5N1 is a biosafety level 3+ pathogen. That means in a laboratory setting, this virus must only be handled in unique high containment buildings, specially engineered with airlocks, double-door access, shower in, shower out, all floors, walls, ceilings sealed and waterproofed. All electric outlets, phone cords, caulked, collared, sealed to prevent any air leaks. All surfaces decontaminated daily. All solid waste incinerated. That is how you’re supposed to handle this virus. That’s biosecurity. In contrast to this, the global industrial poultry industry seems to be breeding viruses like H5N1 at essentially biosafety level zero. So, the poultry industry may not only be playing with fire with no way to put it out, they may be fanning the flames, and firewalls to contain this virus do not yet exist.

Unfortunately, a leading USDA poultry virologist told an international gathering of bird flu scientists, “Unfortunately this level of biosecurity just doesn’t exist in the United States,” and doubts really it exists anywhere in the world. And according to emeritus poultry professor, author of Handbook on Livestock Diseases, standards of biosecurity may actually be in decline in an attempt for the industry to cut costs. Now biosecurity measures as they’re currently practiced are certainly better than nothing, but may not be something we want to stake the lives of millions of people upon for the sake of cheaper chicken.

A pandemic caused by H5N1 or some comparable future bird flu virus has the capacity to trigger one of the greatest catastrophes of all time. So, to decrease the risk of generating increasingly dangerous bird flu viruses, the global poultry industry must reverse course, away from greater intensification by, for example, here, in the annals of New York Academy of Sciences, replacing these large industrial units with smaller farms with lower stock and densities of animals, which could potentially result in less stress, less disease susceptibility, less intense infectious contents, and lower infectious loads across the board.

In 2007, the Journal of the American Public Health Association published an editorial that went beyond just calling for de-intensification of the poultry industry. They questioned the prudence of raising so many chickens in the first place. In their editorial, “Chickens Come Home to Roost,” it is curious that changing the way humans treat animals—most basically ceasing to eat them, or at the very least radically limiting the quantity of them that is eaten—is largely off the radar as a significant preventive measure. Such a change, if sufficiently adopted or enforced, however, even at this late stage, could still reduce the likelihood of the much-feared influenza pandemic. It would even more likely prevent unknown future diseases that, in the absence of the change, may result from farming animals intensively and killing them for food. Yet humanity does not even seem to consider this option. We don’t tend to shore up the levees until after the disaster. Hopefully won’t take a pandemic before we take these recommendations into account. The editorial concludes, “Those who consume animals not only harm those animals and endanger themselves, but they also threaten the well-being of future generations on this planet.”

To switch avian images, it is time for humans to remove their heads from the sand, and recognize the risk to themselves that can arise from their maltreatment of other species. How we treat animals can have global public health implications. It’s not surprising, then, that the American Public Health Association, the largest association of public health professionals in the world, has called for a moratorium on factory farms, urging all federal, state, and local authorities to impose a ban on the building of new intensive livestock operations to protect the health of the local communities in terms of air, water, land contamination, pollution. The prudence of this measure certainly grows with our increasing understanding of the role that these operations play in emerging infectious disease.

I’m often asked how the industry responds to this kind of sentiment from the scientific community? Well, last summer the United Nations released yet another report on the global health risks of intensive animal agriculture. Let me show you that how U.S. agribusiness responded to this report. “Feedstuffs” is America’s leading agribusiness publication, and, in an editorial, responded this way to the FAO research report. “FAO claims to use scientists to generate its reports, but I wonder if those scientists don’t resemble a bearded guy living in a cave in Pakistan, who wants the U.S. on its knees?” All too typical of the kind of “you’re with us or against us” industry attitude, unfortunately. Now, this is an extreme example.

There are those within industry who can take a step back and look at the longer-term view. Avian health expert and longtime industry insider, Ken Rudd, wrote a really candid article in Poultry Digest called “Poultry Reality Check Needed.” Drawing on his 37 years’ experience from within the poultry industry, he concluded with these prophetic words. He said, “Now is the time to decide. We can go on with business as usual, charging headlong towards lower costs, or we can begin making prudent moves necessary to restore balance between economics and long-range avian health. We can pay now, or we can pay later, but it should be known and it must be said one way or another, we will pay.”

So, cutting down our consumption of chickens and fighting the role of factory farming, as the United Nations has called for, may indeed prevent the emergence of future viruses, but H5N1 has already been hatched, already spread and mutated into a more dangerous form, and now that is endemic in poultry populations across two continents, eradication is unlikely. Dr. Michael Osterholm is the director of the U.S. Center for Infectious Disease Research and Policy, an associate director within the Department of Homeland Security. He tried to describe what an H5N1 pandemic could look like in one of the U.S. leading public policy journals, called Foreign Affairs。 He asked policymakers to consider the devastation of the 2004 tsunami in South Asia. He said, “Duplicate the tsunami in every major urban center and rural community around the planet. Simultaneously add in the paralyzing fear and panic of contagion, and we begin to get some sense of the potential of pandemic influenza.” That’s what he thinks it could be like. A tsunami in every city, every town, everywhere people drowning in their own bodily fluids. Or, we could imagine Katrina. Imagine every city New Orleans around the world at the same time, all perhaps because people insisted on eating cheaper chicken.

The next pandemic may be more of an unnatural disaster of our own making. A pandemic of “even moderate impact may result in the single biggest human disaster ever, far greater than AIDS, 9/11, all the wars of the 20th century, and the tsunami combined, has the potential to redirect world history, as the Black Death redirected European history in the 14th century.” Hopefully, the direction world history will take is away from raising birds by the billions under intensive confinement, so as to potentially lower our risk of us ever being in this precarious place ever again.

My intention today was just to focus on primary prevention, getting to the root cause, but with the unprecedented spread of this truly precedented virus, it is important that everyone be prepared for the next influenza pandemic. So let me just throw out some resources. The CDC has set up an excellent pandemic preparedness website: pandemicflu.gov。 If you click across here, you will find pandemic preparedness checklists for businesses, schools, communities, faith-based groups, all the way down to individual and family preparation, which really focuses on getting everyone right now to stockpile weeks of essential supplies to shelter in place during a pandemic, isolating ourselves and our families in our homes until the danger passes. The U.S. Department of Homeland Security Is now using as a key planning assumption that the U.S. population may be directed to remain in their homes under self-quarantine for up to 90 days per wave of the pandemic, to support social distancing. Kind of like a snow emergency, where you’re just told to stay inside; don’t go out unless it’s an emergency. But instead of lasting a day or two, lasts weeks or even months. Everyone ready to stay in their homes for three months? If we have to go out to the corner store during a pandemic to buy toilet paper or something, we may be bringing back to our family more than just groceries.

Let me end with a quote from the World Health Organization, The Bottom Line. “The bottom line is that humans have to think about how they treat their animals, how they farm them, how they market them— basically the whole relationship between the animal kingdom and the human kingdom is coming under stress. In this age of emerging plagues, we now have billions of feathered and curly-tailed test tubes for viruses to incubate and mutate within billions more spins at pandemic roulette. Along with human culpability, though, comes hope. If changes in human behavior can cause new plagues, well then, changes in human behavior may prevent them in the future.” Thank you.





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