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Abstract Highly pathogenic avian influenza A(H5N1) virus has caused a multistate outbreak among US dairy cattle , spreading across 16 states and infecting hundreds of herds since its onset. We rapidly developed and optimized PCR-based detection assays and sequencing protocols to support H5N1 molecular surveillance . Using 214 retail milk samples from 20 states for methods development, we found that H5N1 virus concentrations by digital PCR strongly correlated with quantitative PCR cycle threshold values ; digital PCR exhibited greater sensitivity. Metagenomic sequencing after hybrid selection was best for higher concentration samples, whereas amplicon sequencing performed best for lower concentrations. By establishing these methods, we were able to support the creation of a statewide surveillance program to perform monthly testing of bulk milk samples from all dairy cattle farms in Massachusetts , USA, which remain negative to date. The methods, workflow, and recommendations described p...

Abstract Highly pathogenic avian influenza viruses (HPAIV) of subtype H5N1 (clade 2.3.4.4b) have crossed the species barrier and caused a mastitis-like infection in dairy cows . The high levels of infectious virus found in the milk raised considerable concerns about the safety of raw milk products . This study examined the effect of temperature and pH on the stability of HPAIV and low-pathogenic avian influenza viruses (LPAIV). We found that H5N1 HPAIV remained infectious in milk at 4 degrees Celsius for four weeks , with slow decreases at 21 degrees Celsius, and complete inactivation at 37 degrees Celsius after four weeks . H5N1 LPAIV was stable at 50 degrees Celsius for 30 minutes but inactivated at higher temperatures (55 degrees Celsius for 10 minutes, 60 degrees Celsius for 1 minute, or 72 degrees Celsius for 30 seconds). At pH levels between 6 and 10 , the virus remained stable but was partially inactivated at pH 5.0 and completely inactivated at pH 4.0. During yogurt production,...

Abstract We measured stability of infectious influenza A(H5N1) virus in irradiated raw milk and wastewater and on surfaces . We found a relatively slow decay in milk , indicating that contaminated milk and fomites pose transmission risks . Although the risk is low, our results call for caution in milk handling and disposal from infected cattle. Source: US Centers for Disease Control and Prevention,  https://wwwnc.cdc.gov/eid/article/31/4/24-1615_article ____

Abstract The recent spillover events of highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b to dairy cattle , and high viral shedding in the milk from infected animals, has created concern that milk and dairy products could be a route for human infection . It has been demonstrated that pasteurization is effective in inactivating A(H5N1) in milk. However, multiple dairy products are made with unpasteurized but thermised milk . The aim of this study was to examine whether some conditions commonly used for thermisation are effective against inactivation of A(H5N1) in whole milk. For this purpose, we artificially inoculated whole raw cow milk with 6.5 log10 EID50 A(H5N1) and heated for 15 seconds at 60°C, 63°C and 66°C , the viral infectivity was tested using embryonated chicken eggs. We observed over 4 and 5 log10 reduction in viral infectivity at 60°C and 63°C, respectively. The viral infectivity was reduced to below the detection limit at 66°C. We also calculated the D-value...

Abstract The spillover of highly pathogenic avian influenza H5N1 into dairy cattle has raised concerns over the safety of fluid milk . While no human foodborne infection has been reported , this strain has infected dozens of people and milk from infected cows is known to be infectious by ingestion in multiple other species. Investigation into the public health threat of this outbreak is critical . This study uses quantitative risk assessment (QRA) models to represent the United States raw and pasteurized fluid milk supply chains to estimate the risk of human infection from consumption of fluid cow's milk. These models were parameterized with literature emerging from this outbreak, then employed to estimate the H5N1 infection risk and evaluate multiple potential interventions aimed at reducing this risk. The median (5th, 95th percentiles) probabilities of infection per 240-mL serving of pasteurized, farmstore-purchased raw, or retail-purchased raw milk were 5.68E-15 (1.77E-16, 2.98E...

Abstract The spillover of highly pathogenic avian influenza (HPAI) H5N1 virus to dairy cows and shedding of high amounts of infectious virus in milk raised public health concerns. Here, we evaluated the decay and thermal stability spectrum of HPAI H5N1 virus in raw milk. For the decay studies , HPAI H5N1 positive raw milk was incubated at different temperatures and viral titers and the thermal death time D-values were estimated. We then heat treated HPAI H5N1 virus positive milk following different thermal conditions including pasteurization and thermization conditions. Efficient inactivation of the virus was observed in all tested conditions, except for thermization at 50C 10 min . Utilizing a submerged coil system with temperature ramp up times that resemble commercial pasteurizers, we showed that the virus was rapidly inactivated by pasteurization and most thermization conditions . These results provide important insights on the food safety measures utilized in the dairy industry. S...

Background    In March 2024, the USDA confirmed the first case of highly pathogenic avian influenza (HPAI) spreading between dairy cattle herds in the United States.  This followed reports from dairy producers of an unusual illness in their lactating cows over the preceding 2-3 months.  Virus whole genome sequencing and modeling performed by USDA suggested a single spillover of HPAI H5N1, clade 2.3.4.4b, genotype B3.13 from wild birds into dairy cattle likely occurred between October 2023 and January 2024 (1).  Since then, federal, state, and industry partners have collaborated to address the HPAI threat in dairy cattle, resulting in two federal orders and the implementation of the National Milk Testing Strategy (NMTS).  States began enrolling in the NMTS in December 2024, in which they are continuing to conduct or now implementing state-wide bulk tank surveillance and/or milk processing plant silo monitoring.  Nevada was among the first to participate...

Abstract Following reports of HPAI H5N1 infections of dairy cattle in the United States (US) in March 2024, we established a Pan-Canadian Milk network to monitor retail milk in Canada. Milk samples from across Canada that had previously tested negative for influenza A virus (IAV) RNA were tested for the presence of anti-IAV nucleoprotein (NP) antibodies , as an indicator of past infection of dairy cattle. None of the 109 milk samples tested had evidence of anti-IAV NP antibodies. This is consistent with previous findings from our academic group as well as others including federal testing initiatives that have not found any IAV RNA in milk. Although not surprising given that no cases of H5N1 in cattle have been reported in Canada to date, this work further supports that the extensive outbreak in dairy cattle in the US has not extended northward into Canada, and the integrity of the Canadian milk supply remains intact. Source: MedRxIV,  https://www.medrxiv.org/content/10.1101/2025.01...

Abstract In late 2023 an H5N1 lineage of high pathogenicity avian influenza virus (HPAIV) began circulating in American dairy cattle.  Concerningly, high titres of virus were detected in cows’ milk , raising the concern that milk could be a route of human infection . Cows’ milk is typically pasteurised to render it safe for human consumption, but the effectiveness of pasteurisation on influenza viruses in milk was uncertain . To assess this, here we evaluate heat inactivation in milk for a panel of different influenza viruses. This includes human and avian influenza A viruses (IAVs), an influenza D virus that naturally infects cattle, and recombinant IAVs carrying contemporary avian or bovine H5N1 glycoproteins . At pasteurisation temperatures of 63 °C and 72 °C , we find that viral infectivity is rapidly lost and becomes undetectable before the times recommended for pasteurisation ( 30 minutes and 15 seconds, respectively ). We then show that an H5N1 HPAIV in milk is effectively i...

Abstract The recent outbreak of highly pathogenic avian influenza (HPAI) in dairy cows has created public health concerns about the potential of consumers being exposed to live virus from commercial dairy products. Previous studies support that pasteurization effectively inactivates avian influenza in milk and an earlier retail milk survey showed viral RNA, but no live virus could be detected in the dairy products tested. Because of the variety of products and processing methods in which milk is used, additional product testing was conducted to determine if HPAI viral RNA could be detected in retail dairy samples, and for positive samples by quantitative real-time RT-PCR (qRT-PCR) further testing for the presence of live virus. Revised protocols were developed to extract RNA from solid dairy products including cheese and butter . The solid dairy product was mechanically liquified with garnet and zirconium beads in a bead beater diluted 1–4 with BHI media. This preprocessing step was su...

Abstract In 2024, the highly pathogenic avian influenza A H5N1 caused outbreaks in wild birds, poultry, cows, and other mammals in the United States with 61 human cases also reported by the CDC. Detection of influenza A H5 RNA in wastewater has been previously reported in sewersheds in Texas and North Carolina with nearby impacted dairy herds following the emergence of H5N1 in dairy cows. Here, we conduct retrospective testing of total influenza A and H5 hemagglutinin genes in wastewater as well presenting and applying new assays for detection of H1 and H3 genes across a respiratory virus season in an urban California sewershed from September 2023-May 2024. Total influenza A, H1, and H3 were regularly detected, while H5 was first detected in March . We developed a model that uses Monte Carlo simulations and previously published parameters to estimate numbers of infected people, poultry, wild birds, or liters of H5-contaminated milk required to result in measured H5 concentrations in wa...

 {Excerpt} (Xinhua) 13:20, December 17, 2024 LOS ANGELES, Dec. 16 (Xinhua) -- The U.S. state of California has recalled raw milk produced and packaged by Valley Milk Simply Bottled , a local dairy company based in Stanislaus County, due to detection of bird flu virus . The recall order came following the detection of Influenza-A H5N1 (bird flu) virus in samples taken from a raw milk bulk tank at the Valley Milk Simply Bottled dairy farm , said the California Department of Food and Agriculture (CDFA) in a release. The order applies to all "Valley Milk Simply Bottled Raw Cow Milk" and "DESI Milk Raw Cow Milk" distributed in quart, half-gallon, and one-gallon plastic jugs with a code date marked on the container of DEC 23 2024 through DEC 30 2024. CDFA urged consumers not to consume any product remaining in their refrigerators. No illnesses have been reported in the state yet. (...) Source: People's Daily,  http://en.people.cn/n3/2024/1217/c90000-20254910.html   __...