Scientists at the National Institutes of Health (NIAID) have found that heat treatment can significantly reduce the amount of infectious H5N1 virus in raw milk, but small amounts of the virus may remain under certain conditions. This finding is important in light of reported outbreaks of the H5N1 virus in dairy cows in the United States.

美國國立衛(wèi)生研究院（NIAID）的科學(xué)家們發(fā)現(xiàn)，熱處理可大大降低生牛奶中傳染性 H5N1 病毒的含量，但在某些條件下仍會殘留少量病毒。據(jù)報道，美國奶牛中爆發(fā)了 H5N1 病毒疫情，這一發(fā)現(xiàn)非常重要。

Studies have shown that heating raw milk can significantly reduce the amount of H5N1 virus, but it may still remain. Despite the outbreak of cattle flu in the United States, the FDA's ongoing assessment has concluded that commercial milk is safe.

研究表明，加熱生奶可大大降低 H5N1病毒的含量，但仍有可能殘留。盡管美國爆發(fā)了牛流感疫情，但食品及藥物管理局正在進(jìn)行的評估認(rèn)為，商業(yè)牛奶是安全的。

Laboratory experiments show that the amount of infectious H5N1 influenza virus in raw milk drops rapidly after being heated. The research was conducted by scientists at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH).

實驗室實驗表明，加熱處理后，生牛奶中傳染性 H5N1 流感病毒的數(shù)量迅速下降。這項研究由美國國立衛(wèi)生研究院（NIH）下屬的國立過敏與傳染病研究所（NIAID）的科學(xué)家進(jìn)行。
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However, low levels of infectious virus were still detectable in raw milk samples with elevated viral loads after treatment at 72 degrees Celsius (161.6 degrees Fahrenheit) for 15 seconds, one of the standard pasteurization methods used by the dairy industry. However, the study authors stressed that their findings reflect experimental conditions in a laboratory setting and are not identical to the large-scale industrial raw milk pasteurization process. The results were published June 13 in the New England Journal of Medicine.

然而，在 72攝氏度（161.6華氏度）的條件下處理 15 秒（這是乳制品行業(yè)使用的標(biāo)準(zhǔn)巴氏殺菌法之一），病毒含量較高的生奶樣本中仍能檢測到少量傳染性病毒。不過，該研究的作者強(qiáng)調(diào)，他們的發(fā)現(xiàn)反映的是實驗室環(huán)境下的實驗條件，與大規(guī)模工業(yè)化的生奶巴氏殺菌過程并不完全相同。研究結(jié)果于 6 月 13 日發(fā)表在《新英格蘭醫(yī)學(xué)雜志》上。
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In late March 2024, U.S. officials reported an outbreak of a highly pathogenic avian influenza virus, called HPAI H5N1, in dairy cows in Texas. To date, 95 herds in 12 states have been affected, and three human cases have been found in farm workers with conjunctivitis. While the virus has not so far genetically demonstrated the ability to spread between people, public health officials are closely monitoring dairy cows as part of pandemic preparedness efforts.

2024 年 3 月下旬，美國官員報告在得克薩斯州的奶牛中爆發(fā)了名為高致病性禽流感 H5N1 的高致病性禽流感病毒。迄今為止，已有 12 個州的 95 個牛群受到影響，在患有結(jié)膜炎的農(nóng)場工人中發(fā)現(xiàn)了 3 例人感染病例。雖然到目前為止，該病毒還沒有在基因上顯示出在人與人之間傳播的能力，但公共衛(wèi)生官員正在密切監(jiān)測奶牛的情況，作為大流行病防備工作的一部分。

Given limited data on the susceptibility of avian influenza viruses to pasteurization methods used by the dairy industry, scientists at NIAID's Rocky Mountain Laboratories sought to quantify the stability of H5N1 viruses in raw milk when tested at different intervals at 63°C (145.4°F) and 72°C, the temperatures most commonly used in commercial dairy pasteurization processes. The scientists isolated highly pathogenic avian influenza H5N1 viruses from the lungs of a mountain lion that died in Montana. They then mixed these viral isolates with samples of raw, unpasteurized milk and heat-treated the milk at 63°C and 72°C for different periods of time. The samples were then cultured and tested to determine whether, and if so, how much live virus remained.

鑒于有關(guān)禽流感病毒對乳制品行業(yè)使用的巴氏殺菌法的敏感性的數(shù)據(jù)有限，NIAID 洛基山實驗室的科學(xué)家們試圖量化生牛奶中 H5N1 病毒在 63℃（華氏 145.4 度）和 72℃（商業(yè)乳制品巴氏殺菌過程中最常見的溫度）的不同時間間隔下進(jìn)行檢測時的穩(wěn)定性。科學(xué)家們從蒙大拿州一頭死亡山獅的肺部分離出了高致病性禽流感 H5N1 病毒。然后，他們將這些病毒分離物與未經(jīng)巴氏殺菌的生牛奶樣本混合，并在 63℃ 和 72℃ 下對牛奶進(jìn)行不同時間段的熱處理。然后對樣本進(jìn)行細(xì)胞培養(yǎng)和檢測，以確定是否殘留有活病毒，如果有，殘留多少。

They found that a temperature of 63°C produced a significant reduction in infectivity levels of H5N1 virus (1010-fold) within 2.5 minutes, and noted that 30 minutes of standard bulk pasteurization eliminated infectious virus. At 72°C, they observed a 104-fold reduction in infectious virus within 5 seconds, however, in one of three samples, very low levels of infectious virus were still detected after heat treatment for up to 20 seconds. The authors noted: "This finding suggests that relatively low but detectable amounts of H5N1 virus may still be present in milk after heating at 72°C for 15 seconds if initial viral levels are sufficiently high."

他們發(fā)現(xiàn)，63℃ 的溫度可在 2.5 分鐘內(nèi)使 H5N1 病毒的感染性水平顯著下降（1010 倍），并指出 30 分鐘的標(biāo)準(zhǔn)散裝巴氏殺菌可消除感染性病毒。在 72℃下，他們觀察到傳染性病毒在 5 秒鐘內(nèi)減少了104 倍，然而，在三個樣品中，有一個樣品在加熱處理長達(dá) 20 秒鐘后仍檢測到極少量的傳染性病毒。作者指出："這一發(fā)現(xiàn)表明，如果初始病毒水平足夠高，72℃加熱 15 秒后，牛奶中仍有可能存在相對少量但可檢測到的 H5N1 病毒。"

The scientists emphasize that their measurements reflect experimental conditions and should be replicated by direct measurements of infected milk in commercial pasteurization facilities, and that no conclusions should be drawn about the safety of the U.S. milk supply. In addition, a limitation of their study was the use of raw milk samples spiked with H5N1 virus, and raw milk from cows infected with H5N1 influenza may have a different composition or contain cell-associated virus, which could affect the thermal effect. The authors conclude that while highly pathogenic avian influenza H5N1 viruses have caused enteric infections in several mammals, it remains unknown whether ingestion of live H5N1 virus in raw milk can cause illness in humans.

科學(xué)家們強(qiáng)調(diào)，他們的測量結(jié)果反映的是實驗條件，應(yīng)在商業(yè)巴氏殺菌設(shè)備中對受感染牛奶進(jìn)行直接測量后再進(jìn)行復(fù)制，不應(yīng)據(jù)此對美國牛奶供應(yīng)的安全性得出任何結(jié)論。此外，他們研究的局限性在于使用了添加 H5N1 病毒的生乳樣本，而來自感染 H5N1 流感奶牛的生乳可能具有不同的成分或含有細(xì)胞相關(guān)病毒，這可能會影響熱效應(yīng)。作者總結(jié)說，雖然高致病性禽流感 H5N1 病毒已在幾種哺乳動物身上發(fā)生過腸道感染，但攝入生牛奶中的活 H5N1 病毒是否會導(dǎo)致人類患病仍是未知數(shù)。

To date, the U.S. Food and Drug Administration (FDA) has concluded that all evidence continues to indicate that the commercial milk supply is safe. While laboratory benchtop studies provide important, useful information, their limitations pose challenges for extrapolating to real-world commercial processing and pasteurization. The FDA conducted an initial survey of 297 retail dairy products collected at retail locations in 17 states and representing products produced at 132 processing sites in 38 states. All samples were negative for the virus. These results highlight the opportunity for additional studies to closely replicate real-world conditions. The FDA is working with the U.S. Department of Agriculture on pasteurization validation studies, including the use of homogenizers and continuous-flow pasteurizers. We will share additional results as they become available.

迄今為止，美國食品和藥物管理局（FDA）的結(jié)論是，所有證據(jù)仍然表明商業(yè)牛奶供應(yīng)是安全的。雖然實驗室臺式研究提供了重要、有用的信息，但其局限性對推斷現(xiàn)實世界中的商業(yè)加工和巴氏殺菌提出了挑戰(zhàn)。美國食品和藥物管理局對在 17 個州的零售點(diǎn)收集的 297 個零售乳制品進(jìn)行了初步調(diào)查，并代表了在 38 個州的 132 個加工點(diǎn)生產(chǎn)的產(chǎn)品。結(jié)果發(fā)現(xiàn)，所有樣品中的病毒均為陰性。這些結(jié)果突出表明，有機(jī)會進(jìn)行更多的研究，以密切復(fù)制現(xiàn)實世界的條件。FDA 正在與美國農(nóng)業(yè)部合作開展巴氏殺菌驗證研究，包括使用均質(zhì)器和連續(xù)流巴氏殺菌器。一旦有了更多結(jié)果，我們將立即公布。