H5N1 Flu Update - Oct 2024
In recent months I’ve mentioned it looks to me like H5N1 influenza is beginning to be able to transmit from human to human. Not often, not easily, not enough to say it is a regular occurrence. It’s still too early for science to say we have definitive proof of the virus making that leap. Right now, we still have only sporadic cases that look like transmission from person to person. The Missouri case with no known animal exposures, the illnesses of six people who attended to that case and a household contact? That’s difficult to explain without human to human transmission. Officials are trying to do so but haven’t come up with an alternative explanation that sounds adequate.
We are getting a clearer picture of how the virus is changing. The title of the 28 October 2024 news release from the USA’s National Institute of Allergy and Infectious Diseases (NIAID, part of the National Institutes of Health) is
Bovine H5N1 influenza from infected worker transmissible and lethal in animal models
The article is based on two studies published in Nature. (They are referenced at the end of the news release.) The article is brief and relatively easy to understand for people who don’t want to wade through all the details.
The studies were done on H5N1 influenza virus isolated from a farm worker whose main symptom was conjunctivitis (inflamed eyes). Key points:
It was a strain of the virus with a specific mutation often seen in strains that can replicate in mammals.
Although the farm worker got it from working with cows, it also readily infected ferrets and mice in the laboratory.
Flu more closely resembles how it goes in humans when it is given to ferrets rather than mice. When ferrets got a high viral load, they all died. In a previous study when ferrets were given flu of an earlier strain from cows, it wasn’t always lethal.
It was able to spread between ferrets in separate enclosures through the air, although with “limited efficiency.”
In the laboratory, it replicated readily in human corneal and lung tissue.
With the virus able to do all of that, why wasn’t the farm worker severely ill? Scientists believe it’s because the farm worker got only a light viral load (not many viral particles) through the eyes rather than into the lungs. I say they believe this because that’s as far as science has gotten so far—it is only a hypothesis that has not been proven.
There is a nugget of good news in the article. The virus is susceptible to at least a couple of antiviral drugs, favipiravir and baloxavir marboxil. You may have noticed that H5N1 flu is sweeping through herds of cattle in multiple states in the USA. Ideally, we could treat cows in infected herds and clamp down on opportunities for the virus to evolve nastier capabilities.
To do so, herds have to be tested. Many farmers are reluctant to allow testing of their cows, concerned about financial impact on their farms, especially if any animals are found to be infected. Instead, growing numbers of cows are dying of flu. In some instances, their carcasses lie where they fall for a few days, unshielded from scavengers.
Chances are that you’ve had some version of the flu once or twice. Miserable, even scary, isn’t it? Even when it isn’t a new strain that has devastated other species.
We certainly should not invite another pandemic on top of the one we already have. We know what we should be doing, as a civilization, to fend off a pandemic of H5N1 flu. Farm workers (and other people who work with potentially infected animals such as zookeepers or veterinarians) should have appropriate personal protective equipment. Susceptible animals and potentially exposed people should be tested and any that are infected should be treated.
What can you and I do to protect ourselves in case H5N1 finds the key to easy human-to-human spread?
Getting vaccinated will help us fight infection, but against “bird flu” it doesn’t help enough. The annual flu vaccine isn’t tuned against H5N1 variants. It’s tuned against types of flu that have been circulating among people. Too many people would still get frightfully ill despite the vaccine. We have to do more than get our flu shots.
So let’s not catch it if we can avoid it.
The same non-pharmaceutical interventions that diminish our potential exposure to SARS viruses work against influenza viruses too. If your habits are COVID conscious, you’re also doing the right things to avoid catching flu—of any kind, H5N1 or more ordinary.
It’s a classic Keep Calm And Carry On situation, or should be. What we’ve already learned to do is exactly what we need in the event that H5N1 becomes capable of pandemic spread. We know how to block it. During COVID lockdowns we drove one strain of flu to extinction. We can do it to H5N1.
But it would be nice if we never let matters reach a point where we have to.
—
Postscript: After I wrote this, I saw breaking news that H5N1 flu has turned up in a pig at a backyard farm in Oregon. Flu pandemics in humans usually start in birds or pigs, and now this strain has infected both. We are lucky it happened at a mini-farm instead of a larger farm that is in the commercial supply chain with lots of animals and people. This incident at such a small farm is unlikely to spark a pandemic. But it’s a warning sign. We should heed it.