H5N1 (Avian Influenza) Risk Assessment
What is the risk? What do the latest data demonstrate?
Summary of key points :
Avian influenza A (H5N1) has been endemic in many parts of the world for decades in a wide variety of bird species. Therefore, this virus cannot be eradicated.
Infections with the highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b) virus have resulted in the death of millions of domestic birds and thousands of wild birds in the U.S. since January, 2022. A large fraction of the millions of domestic birds that have died were intentionally “culled” (slaughtered and buried) in a futile effort to reduce further spread.
Throughout the current avian outbreak, spillovers of the virus to mammals have been frequently documented.
Migratory waterfowl are often infected with influenza (including H5N1) and shed large amounts of the virus in their stool (and into open water sources) when infected.
It is a well-established fact that all influenza A viruses, including H5N1, exhibit exceptional stability in wet environments, including open water sources.
There remains no evidence of sustained human-to-human transmission of H5N1 clade 2.3.4.4b.
No human deaths or hospitalizations have been reported from the currently circulating strain of H5N1. Per a Nature Magazine News Brief: A dairy worker in Texas was infected and recovered. The worker’s only symptom was eye inflammation and viral levels in their nose were low, suggesting that they don’t have a respiratory infection, according to the CDC. The virus that the worker contracted is closely related to the strains found in dairy cattle in Texas, with one notable distinction: the worker’s variant has a mutation that is linked to more efficient spread in mammals. The presence of the mutation in the human sample was not surprising; it has appeared many times, including in foxes and cats infected with H5N1.
Cattle can be infected with the currently circulating strain of H5N1.
There is no evidence that the strain of H5N1 currently circulating in North American birds (and cattle) is highly pathogenic or lethal in either cattle, humans or other mammals.
When infected with H5N1, cattle develop mild, transitory symptoms, which include decreased milk production.
Milk pasteurization destroys the infectivity of H5N1 and other influenza viruses.
Recent findings indicate that the cells lining the milk-producing glands and ducts of cattle can produce large amounts of H5N1 when a lactating cow is infected.
There is no history of widespread cattle testing for influenza virus infection until recently, so there is no evidence for or against alternative hypotheses that this infection is either a new or a longstanding phenomenon.
The cells lining a cow udder's milk-producing glands and ducts display receptors that can bind to both human and avian-type influenza viruses. This has most likely been true for thousands of years. Therefore the risk of further evolution of H5N1 to a more human-infectious and pathogenic form consequent to cattle infection remains unchanged from prior decades.
Since cows frequent open water sources shared with a wide range of waterfowl, it is reasonable to hypothesize that cows have been infected by avian influenza for as long as there has been contact (waterborne or otherwise) between them and these viruses (which were first detected in China in 1996).
Not surprisingly, H5N1 (clade 2.3.4.4b) persists as an infectious virus for a functionally relevant time on solid surfaces, including the rubber and stainless steel surfaces associated with modern milking machines—particularly in moist or high-humidity environments. Claims that milking machines are spreading H5N1 in cattle are speculative and should be considered unproven hypotheses at this time.
Studies specifically designed to detect aerosol transmission between cows have not found any evidence of airborne transmission of H5N1 (clade 2.3.4.4b) in cattle.
Contrary to various irresponsible, speculative articles in corporate media (NYT, Business Insider, etc.), there have been no cases of Avian Influenza disease in humans attributed to the consumption of unpasteurized milk (or cheese).
With the current array of numerous safety measures, infectious H5N1 virus in milk is unlikely to enter the food supply.
“Moderna Inc. secured nearly $200 million from the US government to speed development of an mRNA vaccine for pandemic influenza as a dangerous strain of bird flu sweeps through the nation’s dairy farms, fueling concern about a budding health crisis.” (Bloomberg News)
Moderna likely isn’t the only pharmaceutical company that will reach a contract to develop mRNA vaccines for pandemic flu. The US anticipates making additional announcements about other awards.
The US Government is also sponsoring two H5N1 (clade 2.3.4.4b) vaccine candidates based on already approved H5N1 influenza vaccine products, and is testing them with GSK Plc, Sanofi SA and CSL Seqirus. There are hundreds of thousands of pre-filled syringes already on hand, and the US has tasked CSL with filling-and-finishing another 4.8 million vaccine doses.
Threat Assessment
The “high pathogenicity” H5N1 Avian Influenza (high path for birds, not for cows, humans, or other mammals) currently circulating in North America does not represent a significant current health threat to either cows or humans relative to other widespread health threats, infectious disease-based or otherwise.
There are two US-licensed H5N1 vaccines based on established, licensed influenza vaccine technology. While not without any adverse events, the safety profile of these products and the underlying technology is far superior to the adverse event profile associated with COVID mRNA vaccines.
Worldwide, the current regulatory position has long been that “updated” versions of influenza vaccines reflecting new but related influenza variants can be produced and market-authorized without additional prospective clinical trials. Typically, there is a requirement to monitor the efficacy of these modified products by monitoring antibody titers (typically using some variant of the hemagglutination or viral neutralization tests) produced in vaccinated individuals. Post-marketing safety evaluations of these variant vaccines are rare. Sometimes, there may be a post-marketing evaluation of field effectiveness (protection from infection and/or disease).
It is a judgment call whether the hundreds of millions of dollars being spent on developing, testing, and stockpiling the H5N1 (clade 2.3.4.4b) vaccine is a worthwhile public health investment relative to alternative investments of these funds to address other public health (or other types of) threats.
I do not see a significant present threat or danger to human health from H5N1 (clade 2.3.4.4b) at this point, and the USG/HHS already has two H5N1 vaccines in the stockpile. This includes what are probably a sufficient number of doses for ring vaccination if this variant does develop or demonstrate sustained human-human transmission, with warm base manufacturing capabilities to produce large doses if necessary.
This threat assessment may change in the event that either sustained human-human transmission or significant levels of H5N1-associated human sickness and death are detected. However, this has not occurred to date despite the current variant circulating widely in birds since at least 2022, so the risk appears modest to non-existent.
In my opinion, the current data indicate that the ongoing fear-mongering (FearPorn) by corporate media, academics, politicians, and government employees concerning H5N1 (clade 2.3.4.4b) is grossly irresponsible and constitutes yet another example of Psychological Bioterrorism.
Those practicing Psychological Bioterrorism should be shamed and marginalized.
Anyone promoting or participating in Psychological Bioterrorism regarding H5N1, including marketing unlicensed supplements or kits claiming to prevent or mitigate H5N1 infection and disease in humans, and their host institutional affiliations should be suspected of having some conflict of interest.
References with links:
Huge amounts of bird-flu virus found in raw milk of infected cows (Nature, paywall)
How Does Bird Flu Spread in Cows? Experiment Yields Some ‘Good News.’ (NY Times, paywall)
A new study suggests a culprit in bird flu's rapid spread through US cattle, and how to stop it. Business Insider
Persistence of Influenza H5N1 and H1N1 Viruses in Unpasteurized Milk on Milking Unit Surfaces (CDC “Emerging Infectious Diseases” - not peer-reviewed)
From birds to mammals: spillover of highly pathogenic avian influenza H5N1 virus to dairy cattle led to efficient intra- and interspecies transmission (preprint, not peer-reviewed)
Influenza H5N1 and H1N1 viruses remain infectious in unpasteurized milk on milking machinery surfaces (preprint, not peer-reviewed)
The avian and human influenza A virus receptors sialic acid (SA)-α2,3 and SA-α2,6 are widely expressed in the bovine mammary gland (preprint, not peer-reviewed)
The mammary glands of cows abundantly display receptors for circulating avian H5 viruses (preprint, not peer-reviewed)
Characterization of highly pathogenic avian influenza virus in retail dairy products in the US (preprint, not peer-reviewed)
Pasteurization temperatures effectively inactivate influenza A viruses in milk (preprint, not peer-reviewed)
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