Highly pathogenic avian influenza (HPAI) viruses have occasionally infected humans, often with severe outcomes. Reports of HPAI in dairy cattle and the detection of high titres of the virus in cattle milk in the United States are therefore a cause for concern. Documented human infections linked to cattle infections, though mild, highlight the urgent need for enhanced biosecurity and vigilant monitoring.

Highly pathogenic avian influenza (HPAI) viruses of the A/goose/Guangdong/1/1996(H5N1) lineage (HPAI H5 viruses) have taught us many lessons since their emergence in 1997:

1. 1.

   Historically, outbreaks of HPAI viruses were limited to terrestrial poultry and controlled by culling of infected flocks in many countries. However, HPAI H5 viruses became established in wild water birds of the order Anseriformes (that is, ducks, geese and swans, the main reservoir of avian influenza A viruses). These viruses have caused multiple outbreaks in species of the order Charadriformes (that is, gulls, terns and shorebirds), and, in recent years, have infected an increasing number of raptor and peridomestic species. This expansion in host range has been paralleled by HPAI H5 virus spread across several continents.

2. 2.

   Avian influenza A viruses are typically benign in their natural reservoir; however, several HPAI H5 virus outbreaks in species of the orders Anseriformes and Charadriformes have caused mass mortality of infected birds.

3. 3.

   HPAI viruses had rarely infected mammals. Recently, however, HPAI H5 viruses have infected an increasing number of mammalian species, mostly scavengers and animals of prey¹. While mammalian infections with HPAI viruses were limited to individual animals, recently, there have been reports of HPAI H5 infections of large groups of mammals including seals along the northeastern coast of the USA, mink in a mink farm in Spain and sea mammals in South America.

4. 4.

   HPAI H5 viruses were not known to transmit among mammals; however, HPAI H5 virus transmission among mammals may have occurred during outbreaks in mink in Spain in 2022 and sea lions and seals in South America. In laboratory settings, a mink HPAI H5 virus was transmitted via respiratory droplet to exposed ferrets in one study, whereas in another study conducted with a different mink virus isolate, respiratory droplet transmission among ferrets was not detected.

高致病性禽流感（HPAI）病毒偶尔会感染人类，通常会造成严重后果。因此，有关奶牛高致病性禽流感的报告以及在美国牛乳中检测到高滴度病毒的情况令人担忧。有记录的人类感染与牛感染有关，虽然轻微，但凸显了加强生物安全和警惕监测的迫切需要。

A/goose/G​​uangdong/1/1996(H5N1)谱系的高致病性禽流感(HPAI)病毒（HPAI H5病毒）自1997年出现以来给我们带来了许多教训：

1. 1.

   
   从历史上看，高致病性禽流感病毒的爆发仅限于陆生家禽，并在许多国家通过扑杀受感染鸡群来控制。然而，HPAI H5 病毒在雁形目野生水禽（即鸭、鹅和天鹅，甲型禽流感病毒的主要宿主）中定居。这些病毒已在鸬鹚目的物种（即海鸥、燕鸥和滨鸟）中造成多次爆发，并且近年来感染了越来越多的猛禽和家禽物种。宿主范围的扩大与 HPAI H5 病毒在几大洲的传播同时发生。

2. 2.

   
   甲型禽流感病毒在其自然宿主中通常是良性的；然而，雁形目和鸫形目物种中的几次 HPAI H5 病毒爆发已导致受感染鸟类的大规模死亡。

3. 3.

   
   HPAI病毒很少感染哺乳动物。然而，最近，HPAI H5 病毒感染了越来越多的哺乳动物物种，其中大部分是食腐动物和捕食动物¹ 。虽然哺乳动物感染高致病性禽流感病毒仅限于个体动物，但最近有报道称，大群哺乳动物感染高致病性禽流感病毒，包括美国东北海岸的海豹、西班牙水貂养殖场的水貂和南美洲的海洋哺乳动物。 。

4. 4.

   
   据了解，HPAI H5 病毒不会在哺乳动物之间传播；然而，HPAI H5病毒在哺乳动物之间的传播可能发生在2022年西班牙水貂以及南美洲海狮和海豹爆发期间。在实验室环境中，一项研究中，水貂 HPAI H5 病毒通过呼吸道飞沫传播给暴露的雪貂，而在另一项使用不同水貂病毒分离株进行的研究中，未检测到雪貂之间的呼吸道飞沫传播。