Influenza A Is Still The Top Dog

Sorry COVID, you have been moved to the end of the post today

It’s probably too soon to say this, but in the grand scheme of viruses SARS2-COV was a light weight. It caused so much havoc only because it was brand new to our species, and so highly contagious. We have just witnessed the terrible effects when a fairly mild (on a population level), but novel pathogen with only a 1% overall mortality rate infects everyone. In the early days of the HIV epidemic, when it was obvious that the disease was 100% fatal, and also that its method of contagion was limited to blood and body fluid exposure, I often thought humanity had dodged quite a big bullet. What if HIV had been a respiratory virus, instead of something transferred only with intimate contact? New Yorkers will remember the panic in the Hamptons at the mere suggestion that perhaps the disease could be transmitted by mosquitos. COVID carried off (and continues to snuff out) primarily the very old and the sick, mostly sparing the young and healthy. It didn’t have to be that way. The Influenza pandemic of 1918 had a significantly higher mortality rate of perhaps 10%, and murdered the young and healthy, with unusually high mortality in 20-40 year olds. Older folks up to age 65 had some degree of residual immunity from infection by a related virus years earlier, and fared much better than expected. That 1918 pandemic virus H1N1 was of Avian origination, and descendants of it continue to circulate in the human population today.

What if the biggest thing we have to worry about isn’t Russia or China? What if the biggest concern isn’t inflation, which octogenarian sits in the Oval Office, the Culture War which knows no truce, or which pronoun will get you kudos instead of cancelled? What if a greater concern is the long overdue Influenza A pandemic? That unpleasant possibility could come in the form of a human Influenza A with a significant change in its genome, what virologists call a shift, and a mortality several times higher than that of COVID. Or it could come as an Influenza A virus crossing over from animals and completely new to our species. In that worst case scenario it could be a highly contagious virus with a 30% mortality, and no respecter of youth, or excellent health. Nobody in their right mind wants to think about this now, as we are just emerging from the misery of the last three years; but unfortunately it will happen—if not next month, then next year or perhaps next decade. Amid all the rancor and finger pointing about how mis-guided much of our response to the Pandemic has been, there seems to be a fair amount of agreement that as a society we haven’t learned much at all from the episode; and that calls for investment and study to better prepare for the next pandemic are likely to be ignored.

To quote the Chinese general Sun Tzu (or Rage Against the Machine depending on your outlook), “Know your enemy”. Let’s take a closer look at Influenza A and why it probably is the most successful virus on this planet—I’ll leave exoplanets out for now which may have some truly horrific contenders. Of the four species of Influenza viruses A B C and D, Influenza A is the only one to have both permanent animal reservoirs, and to constantly infects humans. Influenza A is an RNA virus, like SARS2, and like other similar virions its genome mutates at a fairly quick rate. The genetic material of this virus is carried in 8 separate segments which encode its limited number of proteins. Influenza A can change when a copy error is made while replicating its RNA, causing a mutation or drift. More importantly, when 2 different strains of the virus infect the same cell, those 8 large segments of genome can freely re-combine into a completely new virus. In fact this happens all the time, and every possible combination of the 8 different segments is routinely created. Many of these combinations are immediately selected against as they provide no replication or transmission advantage in the species the virus has infected—but every once in a while the virus hits the lottery.

The permanent natural reservoir of Influenza A is wild water fowl, which generally do not develop symptoms. These Avian flu viruses infect pigs (and many other animals) and recombine with Swine flu viruses to create strains capable of infecting humans with sustained person-to-person transmission, thus giving rise to annual Influenza A epidemics. Picture a farm in China where pigs and ducks are being raised and slaughtered for the ideal viral playground. For several decades scientists have been aware of the occasional transmission of different Avian Influenza strains directly to humans, often with severe disease and high mortality—but lacking the ability to transmit person-to-person. Some of these Avian viruses are highly lethal and contagious for other birds, especially domestic fowl species. H5 and H7 strains tend to be these highly pathogenic strains, both for chickens and the rare human cases. We have been following the very devastating zoodemic of H5N1 over the past year, as it has swept across the world killing millions of birds. What is unusual about this current strain of highly pathogenic Avian Influenza A is the extremely wide range and number of mammals it is infecting. (See the prior posting, “Are We Listening to Nature”)

It’s time to bring man’s best friend into the picture. This past week state health departments announced the first 2 cases of dogs dying from H5N1, and also a cat. A bit more background on dogs and Influenza A is necessary for a clear picture of the significance of this. Dogs are quite susceptible to Influenza with specific Canine strains H3N2 and H3N8. The first of these appears to have originated in horses and has now adapted to be specific to dogs, appearing in the US for the first time in 2004. The H3N8 Canine Influenza Virus is avian in origin, also now adapted for dog-to-dog transmission, and first being recognized in the US in 2015, according to the CDC. Not all that many people in the US are intimately exposed to pigs, and given the fact that pigs usually become ill with the infection, at least some forms of human protections are generally in place in the industrial farming of swine. Even fewer people are exposed to the increasing array of wild mammals which have been infected by H5N1. Dogs though are a different story. Right now we have no idea what percentage of dogs which acquire this Avian Influenza H5N1 are even symptomatic. If the virus adapts to dogs and becomes contagious between canines then two things happen. The opportunity for transmission to humans will be dramatically increased (unless you are in the habit of wearing a mask around Fido), and the law of big numbers will be operating as the different Influenza A viruses which infect dogs experiment with recombination—looking for the chance event of a novel strain which becomes transmissible person-to-person. None of us (I presume) are directly involved with public policy, so what should we do with this information? Not being paranoid is a good starting point. Having a genuine understanding of the potential risk, and formulating a general plan of how you would react, and what steps you might take to respond rationally and effectively can only help. There is the option of making your concern known to your elected representatives in Washington—good luck with that.

The COVID story can be summed up in short order. Hospitalizations and deaths in the US continue to decrease as the warm weather season spreads around the country. We are down to about 150 deaths per day, the new normal for the Endemic. The experience in India is far different. XBB.1.16, with the catchy name Arcturus, is continuing its rapid ramp up with 11,000 new cases yesterday, and 50,000 current active cases—that’s the most rapid increase in cases seen there in the past year. Singapore had been averaging 1,400 cases per month, but last week 4,000 new cases emerged, with 30% of them being re-infections. It will take another 2 weeks to see if there is a significant impact on hospitalizations and deaths. We should expect to see a similar increase in the UK very soon. XBB.1.16 has been identified in over 20 countries, but so far in the US there have been so few sequences identified that it is not yet broken out into a separate category by the CDC NowCast data—expect that to change. My guess is this XBB is another Scariant, which will increase cases but have minimal impact on severe disease case numbers. I am also available to choose lottery numbers for a small fee.

Enjoy your weekend. I understand it’s quite warm on the east coast, but here in Telluride it’s snowing briskly. I will get the message if people are interested in non-COVID discussions via the like button at the top of the feed, and through comments which are always welcome.