** Health Security Decoded - July 11, 2024 - US CDC confirms 4th human case of H5N1 linked to dairy cattle outbreak; experts urge more widespread testing of humans, animals, wastewater
Buzz Sawyer
US CDC confirms 4th human case of H5N1 linked to dairy cattle outbreak; experts urge more widespread testing of humans, animals, wastewater
Is H5N1 avian influenza here to stay? Some experts are starting to wonder, worrying that a lackluster government response and little cooperation from US dairy farmers points to the virus becoming endemic in poultry, cows, and other animals, with an ever-present risk of the virus evolving to transmit more easily to and between humans. In the last 30 days, the US Department of Agriculture (USDA) has reported detections of H5N1 avian influenza (2.3.4.4b clade) in 49 dairy cattle herds in 6 states, bringing the total number of affected herds to 146 in 12 states since the outbreak was first reported in March.
On July 3, the US CDC confirmed a fourth human case of highly pathogenic avian flu in a dairy farm worker from Colorado, the latest linked to the current outbreak. The person experienced mild symptoms, including conjunctivitis (pink eye). The US has recorded a total of 5 human cases of H5N1 since 2022, with cases reported from 3 states (the first was in a person involved in culling poultry in Colorado). The CDC says the risk to the general public remains low at this time.
Colorado has had the most affected dairy herds in the past 30 days. After an outbreak was detected in a poultry flock of 1.7 million birds at a large commercial egg producer in the state, Colorado Governor Jared Polis declared a disaster emergency to free up state resources to help officials and farmers response.
Testing
Bolstering testing strategies for H5N1 is critical to identify and contain outbreaks early. Testing in both dairy herds and workers remains largely voluntary, and social stigma and economic concerns hinder testing efforts. Federal agencies are looking for ways to increase the number and types of tests to effectively detect the disease in cattle and people. Some public health officials have suggested anonymized testing to get a broader picture of the outbreak, but doing so would limit the ability to address transmission at the source. Testing policies vary by state; Michigan recently launched a study to test people exposed to sick cows for H5N1 antibodies but participation rates are unclear. Most experts agree that additional support for state and local public health departments is necessary to boost surveillance, including for wastewater testing programs, and that current efforts are not sufficient.
“If you can’t get it right with something that’s as forgiving as this virus has been, in terms of its inefficiency in infecting humans, it really doesn’t bode well for when the stakes are higher.” – Center for Health Security Senior Scholar Dr. Amesh Adalja
Vaccines
The US Department of Health and Human Services (HHS) last week awarded US$176 million to Moderna to develop an mRNA-based pandemic influenza vaccine. While one of the versions would target H5N1, the mRNA technology would allow manufacturers to quickly adapt vaccines if another flu strain emerged. The US government also secured a fair pricing agreement, which it said will ensure equitable access. The government is working with other pharmaceutical companies, including CSL Seqirus and Sanofi, to develop and stockpile other bird flu vaccines.
Meanwhile, Finland is vaccinating workers at poultry and fur farms and others at high risk against bird flu. Specifically, the nation is using a vaccine design based on the H5N8 avian influenza virus, which is expected to provide some protection against H5N1. Finland’s vaccination campaign is part of a broader European Union initiative, with 14 EU nations agreeing to purchase bird flu vaccines through a plan established by the European Commission. Some experts are wondering why the US government has not offered similar vaccination for its farmworkers, veterinarians, and others at high risk of the disease.
Research & Raw Milk
A study published July 8 in Nature highlights the importance of monitoring and understanding the evolving nature of avian influenza viruses as they adapt to new host species. In the study, researchers demonstrated that H5N1 isolated from infected cow milk spread systemically in mice and ferrets, including to mammary glands. Additionally, the virus was able to bind to sialic acids expressed in human upper airways and inefficiently transmitted to exposed ferrets (25% seroconverted with no virus detection). The virus’s ability to bind to both human- and avian-type receptors warrants further investigation, the researchers said, as past flu viruses that developed the ability to bind to both types have led to human pandemics.
The study also found that mice can become sick after drinking even a small amount of infected raw milk, confirming previous research reported in the New England Journal of Medicine. While there have not been any confirmed human cases of bird flu transmission related to raw milk consumption, public health officials worry it is only a matter of time. Americans appear to have little idea of the dangers of raw milk consumption, according to a recent poll conducted by researchers at the University of Pennsylvania. Several US states, including Delaware, are considering legislation to legalize the sale of raw milk for human consumption despite the risks. And it is not only bird flu that poses a risk. At least 165 people in California were recently sickened with salmonella infections in the largest outbreak linked to raw milk in the past decade.
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