H5N1 Bird Flu update

The highly pathogenic avian influenza H5N1 D1.1 genotype—circulating in water fowl and other wild birds—has led to two severe human cases, one in a teenage girl in British Columbia, the other an older man in Louisiana. This is the same genotype that is killing big cats in the big cat sanctuary right here in Washington state, and that has killed sea lions, and terns, and a variety of other wildlife, large and small. (It is not the B3.13 genotype currently infecting dairy herds and commercial poultry operations.) Both human patients showed mutations in the hemagglutinin part of the virus, one of which occurred in both patients—and both times mutated during the course of their illness, that is, while the virus was replicating inside their bodies, as opposed to them being infected initially with an already mutated virus. CIDRAP and the CDC are good sites to seek out more information.

So what does this mean? This mutation in both cases may possibly have been the reason for increased the severity of the illness in people but has not, yet, increased its ability to spread from person to person.

However, it seems perfectly clear to me that the threat level continues to increase. This D1.1 genotype is everywhere in the wild—and with seasonal flu about to reach its peak, reassortment is looking more and more possible. At which point human to human spread becomes frighteningly likely. As one emergency physician recently phrased it, we are now at Defcon 3 for H5N1. (Actually, I’ve been at Defcon 3 for a couple of weeks. I just wish public health could catch up—if they had been more on the ball a year ago we might never have got to this stage.) We need more stringent testing (of people, herds, and flocks), restriction of movement of livestock, enforcement of personal protective gear for dairy and poultry workers, ramp up of vaccination1, and increased production and dissemination of antivirals, test kits, and PPE.

Edit to add: Thanks to a reader on Bluesky I’ve learnt that the UK is taking a much more proactive approach. Worth reading.

This is a dangerous virus. I’m just going to keep repeating what I’ve been saying for a while:

Get your flu shot if you haven’t had one yetIf you have a friendly physician, get a just-in-case prescription of flu antiviralsBuy some all-in-one test kits that will test for Influenzas A and B and CovidWear a maskWash your handsDo not feed your pets raw food or raw food productsKeep your pets indoors if at all possible and, if not, watch them very carefully and do not let them kill birds—this virus seems to have a two-thirds mortality rate for catsIf they do kill birds, or if you find a dead or dying songbird, wear a mask and gloves before disposing of it safely, and take very great care of then disposing of those gloves and washing thoroughly afterwardsIf that dead of dying bird is wild waterfowl, do not touch it. Do report it. If possible stick around and make sure no one else—or their dogs—touches it.If you become ill inform all your contacts and your healthcare providersIf you become ill try to isolate from your cats If your cat becomes ill call your vet and warn them before taking the cat in

There’s still no reason to panic. There is every reason to be alert. Let’s not have 2025 be a repeat of 2020.

See comment below: there’s an mRNA vaccine specific to H5 in the early test stage—and it worked well when tested against a 2024 human isolate of H5N1 (though I don’t know what clade). ︎