Sigh. I have been avoiding this in hopes that it would go away. But no. It’s here, and it will almost certainly get worse.
I’m not talking politics (though don’t get me started). I’m talking about avian influenza, commonly known as bird flu. Earlier this month, more than 60 Canada geese, ducks, swans, and other birds died, right over in Plymouth, most likely from avian influenza. Island folks should stop worrying about coyotes, and start preparing for the arrival of bird flu. Birds fly. A few miles of ocean aren’t going to keep us protected.
Let’s start by learning basic terminology. Stick with me: It’s just one paragraph of sciencey stuff. There are many different influenza viruses. These are classified into four groups, Types A, B, C, and D. Different types affect different species of animals. All bird flus are Type A, as are most human flus. According to the Centers for Disease Control (CDC), only Type A influenzas are known to cause global influenza pandemics. Then there are subgroups, or strains. These are named based on the kinds of proteins on the surface of the virus. H is for hemoglobin. N is for neuraminidase. Then, because scientists love classifying things, they have also divided avian flu viruses into two groups, based on how sick a variant makes a bird. Those causing mild disease are called “low pathogenic avian influenza” (LPAI). Nastier bugs are called “highly pathogenic avian influenza” (HPAI). And just to make life more interesting, low pathogenic strains can morph and turn into highly pathogenic ones.
That’s what we’ve got now. Highly Pathogenic H5N1. According to the New England Journal of Medicine, HPAI H5N1 virus first emerged in 1997, and was eventually spread to every continent in the world by migrating birds. (Did I mention that birds fly?) In 2021, a subvariant was identified, causing serious illness and deaths in ducks and geese, as well as other wild birds. It has persisted for an unusually long time, and has been infecting more and more kinds of animals. Just for example, in the past year, more than 5,000 sea lions, as well as elephant seal pups, porpoises, dolphins, and otters, died from HPAI H5N1 in Peru. Forty-seven lions, three tigers, and a panther died in a zoo in Vietnam.
Then something even more worrisome happened, in terms of human health. The U.S. Department of Agriculture (USDA) found that dairy cattle were also getting infected. The cows weren’t necessarily getting that sick, but they did show signs of reduced appetite, reduced milk production, and abnormal-appearing milk. And the virus was shed in that milk. Barn cats living on those dairy farms drank raw milk from the infected cows and, surprise, they contracted H5N1. Sadly, cats of all kinds, both wild and domestic, appear to be unusually susceptible to this bug. Like those lions, tigers, and panthers in Vietnam, many barn cats died.
Humans working at these farms were also occasionally getting infected. To date, most cases in people have been fairly mild, but the financial impact is already significant, as the virus reduces milk production, and increases costs to the farmers, who must wear protective clothing to minimize the risk of getting infected themselves. H5N1 has now been found in dairy cattle in 16 states across the U.S.Then H5N1 came for the poultry industry. The virus apparently spread from dairy farms to poultry facilities, resulting in the need for mass culling of birds. More than 17 million chickens are reported to have been euthanized. You have probably already seen the empty shelves in the egg section of the grocery store.
Avian influenza is shed in saliva, mucous, feces, and respiratory secretions of infected animals, and can also be transmitted on inanimate objects. Signs in birds can include difficulty breathing, coughing, sneezing, swelling around the head and eyes, lethargy, incoordination, diarrhea, abnormal eggs, and sudden death. Animals currently known to be susceptible include all kinds of domestic poultry and waterfowl, shorebirds, birds of prey, marine mammals, cows, cats, and people.
So what do we do now? If you keep backyard poultry, keep them contained the best you can. Protect them from contact with wild birds, especially from waterfowl. Wash your hands after handling them. For cat owners, do not feed raw milk or raw or undercooked meat, especially poultry, including commercially prepared raw pet foods. (The CDC suggests humans also eschew raw milk and meat.) Keep outdoor cats away from birds. (Good luck. At least remove your bird feeder.) Signs in cats may include fever, loss of appetite, incoordination, walking in circles, blindness, seizures, copious discharge from the eyes and nose, sneezing, coughing, and death. If your cat shows signs, contact your veterinarian immediately. We will want to use masks and other PPE to protect ourselves and our staff, so please give us a heads-up before you actually bring your cat into the clinic. And talk with your physician about taking precautions yourself, especially if you are immunocompromised.
Remember, human cases are still rare. The CDC has reported 67 human cases total in the U.S., with the highest risk being for people who work with birds, cows, or poultry. But in January 2025, the first human death occurred. This also appears to be the first person to contract the disease from a noncommercial backyard flock and/or wild birds, rather than via employment at a dairy or poultry farm.
So far, there has been no evidence of human-to-human transmission. That’s good news. For now. During the height of the COVID-19 pandemic, there was a meme going around on medically oriented social media. I’m sure you’ve heard the saying, “What doesn’t kill you makes you stronger.” Those of us who have studied virology say, “What doesn’t kill you mutates … and then maybe it kills you.” Many of the safeguards against this rapidly changing scenario and the next possible pandemic risk have just been removed by the new administration. Don’t panic, but stay informed. For more information, go to cdc.gov/bird-flu.
