导读：

1月19日与在美国波士顿的女儿聊天，她说起已经有近两周买不到鸡蛋，蛋液产品也销售一空，原因是美国禽流感疾病带来的影响，当然在2月初超市恢复了鸡蛋供应；1月13日与在禾丰进行家禽技术交流的荷兰皇家德赫斯公司蛋禽专家Arien沟通，他谈到当时在荷兰每只蛋鸡的利润达到了税前27欧元，如此高利润的原因之一，也是因为欧洲禽流感带来的鸡只数减少的影响。可见，禽流感在欧美市场对鸡蛋消费者和养殖从业者都产生了明显的影响。所以本期就禽流感的话题请JAN根据合作伙伴荷兰皇家德赫斯公司的技术观点和他个人阅读的大量文章，组织了这篇短文，请大家尤其是关心禽流感对公共卫生安全影响的人士了解，不必要产生恐慌。

在禽流感作为人畜共患病的风险方面，本文的观点是：目前没有证据表明禽流感可以通过食用任何市售食品（包括受污染的禽类产品）传播给人类。人类感染禽流感的情况仍然罕见，且迄今为止尚未发现人际传播。研究表明，禽流感病毒与禽类受体（α2,3唾液酸）结合，而非人类季节性流感病毒使用的受体（α2,6唾液酸），这是该病毒具有物种特异性且对人类没有危险的原因之一。世界卫生组织（WHO）、欧洲食品安全局（EFSA）和联合国粮农组织（FAO）的多家权威机构将禽流感对普通公众的风险标记为“低”，而对经常接触感染动物的人群风险标记为“低至中度”。相关权威机构会定期评估病例数量和风险水平。

——首席技术官 邵彩梅

文/荷兰皇家德赫斯公司驻禾丰技术总监

    Jan Cortenbach

翻译/总部高级研发经理  张鑫

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）是一种主要在鸟类中传播的高度传染性疾病。低致病性禽流感（Low Pathogenic Avian Influenza, LPAI）的首例病例早在1960年就有报道，而高致病性禽流感（Highly Pathogenic Avian Influenza, HPAI）则于1996年首次在中国鹅群中被报出。该病毒有时也会感染哺乳动物。禽流感主要影响呼吸系统（鼻、口腔和呼吸道）、消化系统或神经系统。该疾病多发于农场饲养的家禽（如鸡、鸭和火鸡），以及几乎所有野生鸟类，包括鸭、鸽子、鹅、海鸥和鹳等。猛禽和其它捕食性动物也可能通过食用患病或死于禽流感的鸟类而感染该病毒。

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. 

禽流感可以通过以下途径传播：动物之间的直接接触（如活禽市场），患病（野生）鸟类的粪便，或疫区农场空气中的粉尘。禽流感主要发生在秋季和冬季，此时野生鸟类正在迁徙。正如预期的那样，过去几周在欧洲不同地区发现了越来越多的禽流感感染病例。该病毒在野生鸟类和商业化饲养的家禽中均有发现。预计在未来几周内，感染风险将系统性增加。由于气温降低、湿度增加以及多雾天气，病毒的存活时间延长，并且更容易传入禽舍。

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，禽流感主要有两种类型：HPAI和LPAI。HPAI对鸟类具有致命性，而LPAI则会引起一系列严重症状，如震颤、鼻窦肿胀、体重下降和产蛋量减少等。LPAI的主要风险在于其可能演变为HPAI。由于商业化养禽场通常是密集饲养，一旦发生疫情将立刻产生大量病例。野生鸟类也可能感染高致病性禽流感病毒，这增加了靠近河流和湿地地区的农场爆发HPAI感染的风险。

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：人畜共患病的风险

禽流感可以从禽类传播给哺乳动物（包括人类），主要通过以下两种途径：

直接来自禽类或受污染的环境

A.最高风险群体是那些食用感染禽类的哺乳动物，例如狐狸、浣熊和猫。

B.通过中间宿主，例如另一只哺乳动物。

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，多个奶牛群被报道出感染了禽流感。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载量，表明禽流感病毒可能通过奶水或挤奶流程而传播（与鸟类主要通过呼吸道传播不同）。巴氏杀菌可以灭活病毒。除了牛之外，其它哺乳动物（如狐狸、羊驼和水貂）也有感染病例报告。目前没有证据表明禽流感可以通过食用任何市售食品（包括受污染的禽类产品）传播给人类。正确处理生肉和其他生食原料、彻底烹饪以及良好的厨房卫生习惯可以预防或降低食品受污染的风险。

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，全球报告了56例新的人类感染禽流感病例。大多数病例在病毒检测或发病前曾接触过家禽、活禽市场或奶牛。人类感染禽流感后，症状通常较轻，可能包括发热、头痛、肌肉酸痛、咳嗽和眼部炎症。在某些情况下，人类感染禽流感可能导致严重疾病，如肺炎、呼吸急促，甚至死亡。这些严重病例主要发生在亚洲地区。

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.

人类感染禽流感的情况仍然罕见，且迄今为止尚未发现人际传播。随着禽流感病毒在全球鸟类种群中的广泛传播，在人们未使用适当防护设备的情况下接触感染动物或其环境时，可能会继续发生零星的传播事件。对病毒基因进行了测序，并监测可能改变人畜共患病潜力或易感性的基因变化。研究表明，禽流感病毒与禽类受体（α2,3唾液酸）结合，而非人类季节性流感病毒使用的受体（α2,6唾液酸）。这是该病毒具有物种特异性且对人类没有危险的原因之一。

包括世界卫生组织（WHO）、欧洲食品安全局（EFSA）和联合国粮农组织（FAO）在内的多家权威机构已将禽流感对普通公众的风险标记为“低”，而对经常接触感染动物的人群的风险标记为“低至中度”。相关机构会定期评估病例数量和风险水平。

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. 

如何预防禽流感在家禽养殖场的传播？

生物安全仍然是防止HPAI病毒从野生鸟类传入家禽养殖场以及在养殖场之间进一步传播的关键因素。以下几个重要方面需要考虑：员工和访客管理、卫生情况、饲料及饲料运输、清洁和消毒等。在生物安全方面，避免与养殖场外的其他鸟类接触至关重要。应避免共享养殖设备及人员，或至少将其控制在最低限度。此外，当有新病例报告时，地方当局可以规定将所有家禽/鸟类（包括商业养殖和家庭散养）圈养在室内。在某些国家，当禽流感出现在家禽养殖场时，当局会采取“扑杀策略”（stamp-out strategy）。根据严格协议，对感染农场及其周边1公里范围内的邻近农场的所有动物进行扑杀。同时，还会实施为期数周的3公里保护区和10公里监控区措施，以防止疫情进一步扩散。疫苗接种是保护家禽免受禽流感侵害的额外措施之一。

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，亚洲地区（包括中国）的蛋鸡已经接种了禽流感疫苗，但该疫苗尚未在欧盟获得批准。欧盟也在开发和评估禽流感疫苗。一项田间研究的初步结果显示出良好前景，研究表明接种疫苗组未发生病毒传播。预计不久将在商业化养殖场开展首批疫苗试点研究。