What is Influenza?
Influenza viruses have always been a challenge to manage because they typically infect multiple species. Birds can become infected by all Influenza A subtypes except two, which have been found only in bats. Only some subtypes are transmissible to humans. Any time a new strain of influenza is found in an unexpected species, there is concern for more widespread disease. Many organizations (CDC, USDA, WHO, etc) monitor influenza closely. Animals act as “mixing vessels” which can create new and more problematic flu viruses. For example, H3N2 started off as an avian only flu strain, but has host-adapted to dogs, and is now endemic in some parts of Asia and the US.
The most concerning influenza strains are “High Path Avian Influenza” (HPAI), which typically spread rapidly and have a high death rate in birds. All HPAI are types H5 or H7, but not all H5 and H7 subtypes are HPAI. Wild birds are often a source, as they travel long distances and easily transmit via virus in bird droppings. The virus can persist for weeks in damp, cool environments like manure.
What is happening now?
Here is the CDC’s H5N1 Bird Flu: Current Situation Summary
At the end of March, the USDA, FDA, and CDC issued an update that confirmed HPAI (H5N1) in dairy herds in Texas, Kansas, and Michigan, with presumed positive test results in Mexico and Idaho. This strain appears to have been introduced from wild birds to the cows. Previous to March H5N1 has only been found in birds, humans, cats, and goats, but this is the first documented case of H5N1 infections in cattle.
Consumable products from infected cows are not a concern for transmission if meat is fully cooked and milk is pasteurized. Raw milk and meat are never safe to consume, both for humans and for pets.
What is currently concerning is there are now preliminary reports of H5N1 transmission to humans and cats. A few humans have had mild disease, mostly conjunctivitis, and some cats have been found with severe disease or dead.
While the media is reporting “100% fatality” for infected cats, this is likely way overblown, as there is huge sampling bias. Only already dead or severely sick cats are being tested, so many mildly affected (or asymptomatic) cats are not “counted.”
What does this mean for you?
If you own a cat, consider limiting exposure to birds. This has been true for years now that HPAI is so widespread, but may be especially important with a new strain we don’t fully understand yet. Keep cats indoors, and limit bird/cat contact by discouraging birds near your home (remove bird feeders, etc). Data is limited, but there have been reports of raw meat transmitting H5N1 to cats, so as always, do not feed raw meat to your pets. Your cat’s lifestyle will help dictate how concerned to be if they come down with symptoms of a cold. If this is an indoor-only cat, this would be less concerning than a kitty who spends a lot of time outside and is a known bird hunter.
What about dogs?
We know dogs can typically get H5N1 stains, so keeping dogs away from birds is probably a good idea. This is especially true for dead birds, which may be tempting for dogs to investigate.
Written by Dr. Zachary Glantz
Medical Coordinator/Veterinarian at Art City Vets
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