導讀：

1月19日與在美國波士頓的女兒聊天，她說起已經有近兩周買不到雞蛋，蛋液產品也銷售一空，原因是美國禽流感疾病帶來的影響，當然在2月初超市恢復了雞蛋供應；1月13日與在禾豐進行家禽技術交流的荷蘭皇家德赫斯公司蛋禽專家Arien溝通，他談到當時在荷蘭每只蛋雞的利潤達到了稅前27歐元，如此高利潤的原因之一，也是因為歐洲禽流感帶來的雞只數減少的影響。可見，禽流感在歐美市場對雞蛋消費者和養殖從業者都產生了明顯的影響。所以本期就禽流感的話題請JAN根據合作伙伴荷蘭皇家德赫斯公司的技術觀點和他個人閱讀的大量文章，組織了這篇短文，請大家尤其是關心禽流感對公共衛生安全影響的人士了解，不必要產生恐慌。

在禽流感作為人畜共患病的風險方面，本文的觀點是：目前沒有證據表明禽流感可以通過食用任何市售食品（包括受污染的禽類產品）傳播給人類。人類感染禽流感的情況仍然罕見，且迄今為止尚未發現人際傳播。研究表明，禽流感病毒與禽類受體（α2,3唾液酸）結合，而非人類季節性流感病毒使用的受體（α2,6唾液酸），這是該病毒具有物種特異性且對人類沒有危險的原因之一。世界衛生組織（WHO）、歐洲食品安全局（EFSA）和聯合國糧農組織（FAO）的多家權威機構將禽流感對普通公眾的風險標記為“低”，而對經常接觸感染動物的人群風險標記為“低至中度”。相關權威機構會定期評估病例數量和風險水平。

——首席技術官 邵彩梅

文/荷蘭皇家德赫斯公司駐禾豐技術總監

    Jan Cortenbach

翻譯/總部高級研發經理  張鑫

Avian influenza (AI) is a highly contagious disease primarily found in birds. The first cases of low pathogenic AI (LPAI) were already reported in 1960, and the highly pathogenic AI (HPAI) was first reported in 1996 in geese in China. Sometimes the virus also infects mammals. Avian influenza affects the respiratory (nose, mouth, and airways), digestive, and/or nervous systems. The disease occurs in poultry raised on farms (like chickens, ducks, and turkeys) and nearly all species of birds found in the wild, including ducks, doves, pigeons, geese, seagulls, and storks. Birds of prey and other predators can also contract the virus by eating birds that fell ill or died of avian flu.

禽流感（Avian Influenza, AI）是一種主要在鳥類中傳播的高度傳染性疾病。低致病性禽流感（Low Pathogenic Avian Influenza, LPAI）的首例病例早在1960年就有報道，而高致病性禽流感（Highly Pathogenic Avian Influenza, HPAI）則于1996年首次在中國鵝群中被報出。該病毒有時也會感染哺乳動物。禽流感主要影響呼吸系統（鼻、口腔和呼吸道）、消化系統或神經系統。該疾病多發于農場飼養的家禽（如雞、鴨和火雞），以及幾乎所有野生鳥類，包括鴨、鴿子、鵝、海鷗和鸛等。猛禽和其它捕食性動物也可能通過食用患病或死于禽流感的鳥類而感染該病毒。

Avian influenza can spread via direct contact between animals (live bird) markets, droppings of infected (wild) birds, or dust in the air of infected farms. AI mainly occurs in autumn and winter, when wild birds are mitigating. As expected, more and more AI infections have been identified over the last few weeks in different European regions. The virus was found in both wild birds and commercially kept poultry. The pressure of infection is expected to systematically increase over the next weeks. Due to lower temperatures, higher humidity, and foggy weather, viruses have a longer survival time and are more easily introduced into poultry houses. 

禽流感可以通過以下途徑傳播：動物之間的直接接觸（如活禽市場），患病（野生）鳥類的糞便，或疫區農場空氣中的粉塵。禽流感主要發生在秋季和冬季，此時野生鳥類正在遷徙。正如預期的那樣，過去幾周在歐洲不同地區發現了越來越多的禽流感感染病例。該病毒在野生鳥類和商業化飼養的家禽中均有發現。預計在未來幾周內，感染風險將系統性增加。由于氣溫降低、濕度增加以及多霧天氣，病毒的存活時間延長，并且更容易傳入禽舍。

As mentioned before, there are two main types of avian influenza, HPAI and LPAI. HPAI is deadly to birds, while LPAI causes several severe symptoms, like tremors, swollen sinuses, decreased weight, and egg production (amongst others). The main concern for LPAI is that it evolves to the HPAI. Since commercial poultry farms usually keep the birds close together, AI outbreaks at such locations affect many birds at once. Wild birds can also contract the highly pathogenic AI variants, which cause a higher risk of HPAI infections at farms located close to rivers and wetland areas.   

如前所述，禽流感主要有兩種類型：HPAI和LPAI。HPAI對鳥類具有致命性，而LPAI則會引起一系列嚴重癥狀，如震顫、鼻竇腫脹、體重下降和產蛋量減少等。LPAI的主要風險在于其可能演變為HPAI。由于商業化養禽場通常是密集飼養，一旦發生疫情將立刻產生大量病例。野生鳥類也可能感染高致病性禽流感病毒，這增加了靠近河流和濕地地區的農場爆發HPAI感染的風險。

Avian influenza: Risk for zoonosis?

Avian influenza can be transmitted from birds to mammals (including humans) mainly in two ways:

Directly from birds or contaminated environments

A. The highest risk applies to mammals that eat infected birds, for example, foxes, raccoons, and cats.

B. Through an intermediate host, such as another mammal

禽流感：人畜共患病的風險

禽流感可以從禽類傳播給哺乳動物（包括人類），主要通過以下兩種途徑：

直接來自禽類或受污染的環境

A.最高風險群體是那些食用感染禽類的哺乳動物，例如狐貍、浣熊和貓。

B.通過中間宿主，例如另一只哺乳動物。

In North America, AI has been reported in several dairy herds. Infection in cattle appears to be centered in the udder. The raw milk from infected cows contained high viral loads, indicating a potential route of transmission via milk and milking procedures (rather than respiratory as in birds). Pasteurization inactivates the virus. Apart from cattle, there are cases reported in other mammalian species, like foxes, alpacas, and minks. There is no evidence that AI can be transmitted to humans through the consumption of any commercially available food products including contaminated poultry products. Safe handling of raw meat and other raw food ingredients, thorough cooking, and good kitchen hygiene can prevent or reduce the risks of contaminated food. 

在北美，多個奶牛群被報道出感染了禽流感。牛感染病毒的部位主要集中在乳房。感染奶牛的生乳中含有高病毒載量，表明禽流感病毒可能通過奶水或擠奶流程而傳播（與鳥類主要通過呼吸道傳播不同）。巴氏殺菌可以滅活病毒。除了牛之外，其它哺乳動物（如狐貍、羊駝和水貂）也有感染病例報告。目前沒有證據表明禽流感可以通過食用任何市售食品（包括受污染的禽類產品）傳播給人類。正確處理生肉和其他生食原料、徹底烹飪以及良好的廚房衛生習慣可以預防或降低食品受污染的風險。

In Q4 of 2024, 56 new cases of AI infection in humans were reported worldwide. Most of these cases had reported exposure to poultry, live poultry markets, or dairy cattle before virus detection or onset of illness. In case a human does get infected with AI, symptoms are generally mild. These symptoms can include a fever, headache, muscle ache, coughing, and eye inflammation. Sometimes AI in humans results in severe illness with pneumonia, shortness of breath, and even fatalities. These cases mainly occur in Asia. 

2024年第四季度，全球報告了56例新的人類感染禽流感病例。大多數病例在病毒檢測或發病前曾接觸過家禽、活禽市場或奶牛。人類感染禽流感后，癥狀通常較輕，可能包括發熱、頭痛、肌肉酸痛、咳嗽和眼部炎癥。在某些情況下，人類感染禽流感可能導致嚴重疾病，如肺炎、呼吸急促，甚至死亡。這些嚴重病例主要發生在亞洲地區。

Human infections with AI remain rare and so far, no human-to-human transmission has been identified. With the extensive circulation of AI viruses in bird populations globally, sporadic transmission to humans is likely to continue occurring in settings where people are exposed to infected animals or their environment without appropriate protective equipment. Viruses are also sequenced and genetic changes that may alter zoonotic potential or susceptibility are monitored. Research has shown that the avian influenza virus binds to the avian receptor (α2,3 sialic acids) and not the receptor used by human seasonal influenza (α2,6 sialic acids). This is one of the explanations why the virus is species-specific and not dangerous to humans.  Several authorities, like WHO, EFSA, and FAO have marked the risk as ‘low’ for the general public and ‘low-to-moderate’ for those who are regularly exposed to infected animals. The number of cases and risks are assessed on a regular basis by the authorities.

人類感染禽流感的情況仍然罕見，且迄今為止尚未發現人際傳播。隨著禽流感病毒在全球鳥類種群中的廣泛傳播，在人們未使用適當防護設備的情況下接觸感染動物或其環境時，可能會繼續發生零星的傳播事件。對病毒基因進行了測序，并監測可能改變人畜共患病潛力或易感性的基因變化。研究表明，禽流感病毒與禽類受體（α2,3唾液酸）結合，而非人類季節性流感病毒使用的受體（α2,6唾液酸）。這是該病毒具有物種特異性且對人類沒有危險的原因之一。

包括世界衛生組織（WHO）、歐洲食品安全局（EFSA）和聯合國糧農組織（FAO）在內的多家權威機構已將禽流感對普通公眾的風險標記為“低”，而對經常接觸感染動物的人群的風險標記為“低至中度”。相關機構會定期評估病例數量和風險水平。

What can be done to prevent avian influenza on poultry farms?

Biosecurity remains a key factor in preventing HPAI virus introduction from wild birds into poultry farms and further between-farm spread. Several important aspects are like employees and visitors, hygiene, feed and feed delivery, cleaning, and disinfection should be taken into account. For biosecurity, it is very important to avoid contact with other birds outside of the farm. Sharing farm equipment and personnel should be avoided or at least kept to a minimum. Furthermore, when new cases are reported, the local authority can govern an obligation to keep all poultry/bird types housed inside (both commercial and backyard). In some countries, the authority follows a ‘stamp-out strategy’ when AI is present on a poultry farm. All animals located at that farm and within a 1 km zone of neighboring farms are culled according to a strict protocol. Furthermore, a 3 km protection zone and 10 km surveillance zone are applied for several weeks. This should prevent further outbreaks from that farm. Vaccination is one of the additional measures to protect birds against AI. 

如何預防禽流感在家禽養殖場的傳播？

生物安全仍然是防止HPAI病毒從野生鳥類傳入家禽養殖場以及在養殖場之間進一步傳播的關鍵因素。以下幾個重要方面需要考慮：員工和訪客管理、衛生情況、飼料及飼料運輸、清潔和消毒等。在生物安全方面，避免與養殖場外的其他鳥類接觸至關重要。應避免共享養殖設備及人員，或至少將其控制在最低限度。此外，當有新病例報告時，地方當局可以規定將所有家禽/鳥類（包括商業養殖和家庭散養）圈養在室內。在某些國家，當禽流感出現在家禽養殖場時，當局會采取“撲殺策略”（stamp-out strategy）。根據嚴格協議，對感染農場及其周邊1公里范圍內的鄰近農場的所有動物進行撲殺。同時，還會實施為期數周的3公里保護區和10公里監控區措施，以防止疫情進一步擴散。疫苗接種是保護家禽免受禽流感侵害的額外措施之一。

Currently, egg-laying birds in Asia, including China are already vaccinated against AI, but the vaccine has not been approved in the EU yet. The EU is also developing and evaluating AI vaccines. The first results from a field study are promising, as they show no transmission of the virus to the vaccinated treatment group. The first pilot studies on commercial farms with vaccines are expected soon.   

目前，亞洲地區（包括中國）的蛋雞已經接種了禽流感疫苗，但該疫苗尚未在歐盟獲得批準。歐盟也在開發和評估禽流感疫苗。一項田間研究的初步結果顯示出良好前景，研究表明接種疫苗組未發生病毒傳播。預計不久將在商業化養殖場開展首批疫苗試點研究。