Seek, and Ye Shall Find

You are more likely to be sickened by one of the top-5 food-borne pathogens than by H5N1, at least as of right now. Some of the largest Salmonella outbreaks were linked to the innocuous bean sprout!

Most of my Substack posts could start with the sentence “I’ve been resisting writing about….” This one is no exception; I actually have been resisting writing about avian flu (H5N1) and cows. In fact, I have been resisting thinking about it, or even reading about it, which is ironic because for many years I researched and wrote about wildlife diseases transmitted to humans through a livestock bridging host. Hmmm. Sounds familiar.

My interest in this subject started in veterinary school, when I joined a project led by my mentor. He studied transmission of brucellosis and tuberculosis through cattle (mostly water buffalo) to humans in Nepal and elsewhere.

That picture, above, is me in my salad days sampling a yak for TB and brucellosis at 15,000 feet at a yak festival. We were interested in disease transmission through milk, though transmission through meat is also possible, particularly with home slaughter. Many people in Nepal do not eat beef, however, because it is a Hindu nation and beef consumption is frowned on (though no longer illegal) and is a culturally divisive issue. Some do eat buffalo and many Tibetan people in Nepal will eat buffalo and yak.

At this festival, though, herders bring their yak down (or used to, I don’t know if it is still going on) and a tradition of the festival was that a knife is used to make a slit in the jugular vein of the yak and festival goers stick a cup under the blood flowing out and drink a cup of blood straight from the vein because it is iron-rich and nutritious. Then they apply pressure and/or mud to pack the vein and clot the wound. All the yak I saw undergo this procedure survived it, at least in the two weeks or so I was there. I was incredibly ill while I was there, not from bacteria or viruses in raw yak blood, but from sleeping in a yurt where a fire burned inside and filled the yurt with smoke, eventually giving me a respiratory illness I thought might kill me. But, here I am, twenty years later, luckier than many who breathe wood smoke every day for most of their lives, significantly shortening their life spans.

Back to American cattle. What is going on? The subject of whether America’s milk supply is safe from H5N1, and whether we are all about to be plunged back into the nightmare of another pandemic, has gotten less traction in media—who are always looking to drive clicks through fear—than I thought it might. So far, at least in my media chambers, the public seems to be mostly shrugging. Maybe they have finally come to terms with the fact that living with other people, and having a food supply dependent on livestock, means potential exposure to pathogens. It was, and will always be, thus.

The New York Times has published some long articles on H5N1, one showing how highly pathogenic (which means highly pathogenic in birds, not in humans) influenza has made its way around the globe in the past 20 years. However, H5N1 is not new, has been on the radar as a potential pandemic pathogen for decades, and has always been able to occasionally infect mammals and humans. We still do not understand well if there is widespread transmission among cows, or whether this is truly an entirely new phenomenon.

In the highly regarded journal Proceedings of the National Academy of Sciences, a paper on mass mortality events (MME) in wildlife notes that disease was historically the largest cause of MMEs.

“Across all animal taxa, causes of MMEs were most often associated with disease (Fig. 3; 26.3%) and were attributed to viral (44.5%), bacterial (18.3%), and fungal infections (12.2%). Human perturbation was the second most common cause of MMEs, accounting for 19.3% of total MMEs, mainly from point source environmental contamination (42.5%). Biotoxicity was the third leading cause of MMEs (15.6%).”

So, is it possible that there were previous large undetected outbreaks of influenza in mammals? Definitely. Is it also possible that now viral outbreaks are interacting with factors such as food shortages and climate change to produce higher mortality in wildlife? Certainly. We just do not know—and the New York Times does not know either, despite their seeming certainty that these flu outbreaks in mammals are unprecedented/novel. As the authors of the PNAS paper wrote “However, it remains unclear whether the increase in the occurrence of MMEs represents a true pattern or simply a perceived increase….and may be associated with increased detectability.”

Back to today’s question- do you need to do anything about the current outbreak, other than avoid media about it, as I have been doing. Here is what our federal agencies said on April 25^th:

“The FDA and USDA have indicated that based on the information currently available, our commercial milk supply is safe because of these two reasons: 1) the pasteurization process and 2) the diversion or destruction of milk from sick cows.”

#1 I agree with. Influenza viruses are unstable to heat/temperature, and the fact that milk supplies are testing positive for viral fragments means little—just as PCR tests for SARS-CoV-2 did not tell you whether you were infectious or just had dead virus in your nose. In fact, some research postulates that one of the reasons that avian influenzas do not survive well in humans is that we have different average body temperatures than birds and that influenza viral reproduction works well only in a narrow temperature range.

#2, however, seems like wishful thinking. There will be many asymptomatic cows and it is unlikely that dairy operations can successfully divert every sick animal, even if they were obviously sick. This has always been the case for multiple infections, which is why milk is tested in bulk and then pasteurized. Particularly in large dairy operations (California’s are the largest, some with more than 100,000 animals), it is not possible to monitor every cow and pull every sick one out of production.

And this brings us to the larger issue of food safety generally. While the USA has a fairly extensive food-safety regulatory apparatus, much of it is bureaucratic, bogged down, and operating as inefficiently as all our other large regulatory agencies (Medicare red tape, anyone?). I would be thrilled if the next president made it a top-agenda item to overhaul agencies such as the FDA, APHIS, and the USDA, all of which badly need it. Dr. Vinay Prasad has written extensively about the FDA and its overly cozy relationship with the pharmaceutical industry, and a similar criticism could be lobbed at the USDA. Large producers probably have way too much influence over food safety regulations. For example, milk producers right now are only being required to test cattle if they move between states. Why not institute a more rigorous testing program, or random sampling for every producer, if you actually want to know whether H5N1 is widespread in the milk supply.

Weak testing programs or not, you are far more likely to be sickened by one of the top-5 food-borne pathogens (Norovirus, Salmonella (non-typhoidal), Clostridium perfringens, Campylobacter and Staphylococcus aureus, than by H5N1, at least as of right now. Salmonella causes the most deaths and recent outbreaks have been linked to “flour, peanut butter, salami sticks, onions, prepackaged salads, peaches, and ground turkey.” Some of the largest outbreaks were linked to the seemingly innocuous bean sprout. The CDC recommends “clean, separate, cook and chill” to reduce food-borne disease and I would add “and then stop thinking about it”. (I recommend Steve Templeton’s book on this topic, Fear of A Microbial Planet.)

This logic applies to H5N1, too. The more they look, the more they will find, and this tells us pretty much nothing about what has changed over time or about our changing—or not changing--risk. Avian influenza viruses have been around forever, humans have kept livestock for thousands of years, and there will always be birds flying overhead and defecating. We just did not have cheap PCR tests to pull the curtain back on the viral-genome swapping that has always gone on and that, in any case, there is no simple way to prevent. Me, I will still be dipping my cookies in a nice cold glass of milk.  

For a contra-opinion to mine, here is YLE’s (Your Local Epidemiologist) take on H5N1. I agree with some of what she writes but disagree with the chicken-little tone and some specific points. For example,  Tamiflu doesn’t work, as multiple evidence reviews have shown, so stock piling it pretty useless. Tamiflu is a perfect example of how bad the approval process is for many therapeutics, as many of the trials were funded by Roche.