H5N1: Dangerous reassortment growing more likely

Image: A colorized electron microscope image released by the National Institute of Allergy and Infectious Diseases shows avian influenza A(H5N1) virus particles (yellow), grown in Madin-Darby Canine Kidney epithelial cells (blue). (CDC / NIAID via The Associated Press)

Three bits of news from this week:

The CDC confirmed the first severe human case of bird flu—the D1.1 genotype found in wild birds and poultry, not the B3.13 genotype infecting dairy cows and other mammals—in the US. The patient, in Louisiana, is hospitalised. (The CDC does not use words like ‘severe’ lightly.) Testing is ongoing, but so far there is nothing to indicate that the virus has changed in any way. Which means your risk is no higher than it’s been. In California: Gov. Gavin Newsom has declared a state of emergency and in Los Angeles, cats are dying (probably from eating infected food—whether provided by people or hunted—but that’s not certain).According to the Seattle Times, two wild cougars on the Olympic Peninsual have been killed by bird flu. Both young males; one tagged, one not; one seemed in the prime of health, barely symptomatic—death was very fast—while the other was so ill it had to be euthanised. They did not infect each other but most likely died because they ate infected prey. On the peninsula, cougars eat from both the forest—everything from birds to mammals—and the sea shore—seabirds, harbour seals, and so on. They are top predators. Given the disease rate among seals and terns and other inhabitants of that area, my guess is that there are many, many cougars now dying or dead on the peninsula, which is worrying because it’s small, genetically isolated population.

It’s very clear that bird flu is now widespread in much of the animal world, at least in birds and mammals. We just have to hope that at some point over this year’s flu season (or next, or the one after) someone infected by H5N1 via an infected animal (because right now H5N1 does not have the ability to easily spread from person to person) does not at the same time become infected with a seasonal flu virus (which does have person-to-person transmission) and provide fertile ground for virus reassortment, with the H5N1 gaining the necessary mutation to enable human transmission.

Given how widespread H5N1 now is, andn how easily flu viruses mutate, I believe we’ll have to be very, very lucky for that not to happen. To me it’s now just a question of when.

But let me repeat: I am not an expert! Let me repeat: we have effective antivirals; we have mostly effective vaccines. There is zero reason to panic. Just stay alert. And remember that some animals are very good at masking illness (it’s a survival strategy for them) so please assume it’s possible to catch the virus from what might seem to be a healthy animal (like your cat that just ate a bird; your backyard chicken; the cow or horse in the next field) and take precautions: Wash your hands; if you’ve been outside among animals, wash your boots before you come in, and change shoes; wear a mask in enclosed spaces; do not eat unpasteurised or raw animal products—cook everything.

Have a happy and healthy holiday.