(Beth Clifton collage)
H5N1, much less deadly than it once was, has spread from pole to pole & from birds to cats & mice
ANNAPOLIS, ATLANTA––No one at either the Program for Monitoring Emerging Diseases [ProMED] or the Centers for Disease Control & Prevention is saying so yet, but the chances of keeping the avian influenza H5N1 from becoming endemic among humans now appear to be slim and none.
Likewise, there no longer appears to be any realistic chance of keeping H5N1 permanently out of even the most intensely confined and closely managed domestic poultry flocks.
(Beth Clifton collage)
Control measures have failed
Reality is that control measures have spectacularly failed.
Poultry infected with H5N1, also known as HPAI, short for Highly Pathogenic Avian Influenza, have been aggressively culled by any and all means possible since the first H5N1 crossover into humans killed six of 18 infected people in Hong Kong in 1997.
More than 100 million chickens, turkeys, and other birds have been culled just on U.S. farms since February 2022.
Despite all that, reality also is that H5N1, carried by many species of migratory birds, is now almost routinely crossing over from birds to mammals, including infecting humans who have intensive occupational exposure to H5N1 in agricultural settings.
(Beth Clifton photo)
The good news
The good news, if it can be called that, is that while the first known H5N1 outbreak killed six of 18 infected humans in Hong Kong in 1997, recent human victims have suffered only mild symptoms, chiefly conjunctivitis, and have quickly recovered.
The most recent reported human H5N1 victims were five workers who culled hens at an egg ranch in Colorado, reported by the Colorado Department of Public Health & Environment on July 14, 2024.
H5N1 earlier in 2024 hit dairy workers in Texas and Michigan.
In between, H5N1 infected dairy cattle across the entire Midwest.
The USDA Animal & Plant Health Inspection Service has now identified H5N1 outbreaks among 139 affected dairy herds in 12 states.
The U.S. Food & Drug Administration in April 2024 told media that testing of 297 pasteurized commercially purchased milk and other dairy products from 38 states found no evidence of live H5N1 virus.
(Beth Clifton collage)
“Check beef cattle!” scientist warns
Jarod Hanson, however, chief content officer for the ProMED program of the International Society for Infectious diseases, on June 13, 2024 asked, “With so many dairy herds affected in such a short timespan, at what point is the USDA actually going to look at beef cattle, either through antigen testing or serology, to determine if this is a dairy issue, or more widespread than we may want to believe?
“Odds are not in our favor that beef cattle haven’t been infected,” Hanson warned. “Until a few months ago, spillover of H5N1 into cows of any kind was viewed as unlikely,” but has happened.
“Yet we continue to ignore millions of beef cattle,” Hanson said, who “are likely at mildly to drastically increased odds of being infected, since they are more likely to be outdoors and are often drinking pond water, with those ponds frequented by a multitude of waterfowl species in many of the impacted states.”
(Beth Clifton collage)
Evolution of a virus
Evident in the evolution of H5N1, as in the evolution of other influenzas and COVID-19, is that the virus has become less lethal in order to spread more rapidly, among a wider range of hosts. This is necessary because dead hosts cannot effectively spread a virus.
Simultaneously, species exposed to a once deadly virus tend to evolve greater resistance to it.
“Endemic,” meaning omnipresent among a species or in a particular location, does not necessarily also mean “epidemic,” meaning widespread large morbidity (illness) and mortality (deaths).
But before a disease becomes endemic to a species or in a particular place, it can cause catastrophic morbidity and mortality, with especially serious consequences, including the possibility of extinctions, among rare and endangered species who may already be just barely surviving in their last fragments of viable habitat.
(Beth Clifton collage)
H5N1 & global warming
This is of particular concern in the parts of the world most affected by global warming.
H5N1 in April 2024 was reported by Christian Lydersen of the Norwegian Polar Institute to have killed a walrus found dead in 2023 on Hopen island in the Svalbard archipelago, well inside the Arctic Circle––unless, that is, the walrus was infected with the closely related avian influenza H5N8.
This would not be much better for walruses, if at all.
The report of the infected walrus followed findings by the Scientific Committee on Antarctic Research that H5N1 had killed a king penguin, an adult gentoo penguin, and at least 20 chicks on South Georgia island, plus another gentoo penguin in the Falkland Islands, 900 miles west.
Humboldt penguin and skua.
(Beth Clifton collage)
Elephant seals & penguins
“Since H5N1 arrived in the Antarctic,” observed Phoebe Weston of The Guardian, “there have been mass deaths of elephant seals as well as increased deaths of fur seals, kelp gulls, and brown skua in the region.
“Previous outbreaks in South Africa, Chile and Argentina show penguins are susceptible to the disease,” Weston wrote. “Since H5N1 arrived in South America, more than 500,000 seabirds have died of it, with penguins, pelicans and boobies among those most heavily affected.”
H5N1 has circulated especially rapidly parallel to the 2020 spread of COVID-19, possibly taking advantage of weakened mammal populations, or of weakened surveillance, as health agencies shifted their focus to combatting COVID-19, which has now killed more than seven million people worldwide, including 1.2 million Americans.
Other victim species have included foxes, seals, alpacas, polar bears, and pumas.
Ellison the elephant seal at Hidden Beach.
(Beth Clifton photo)
Already endemic in many regions
“The Eurasian HPAI H5N1 is becoming endemic in many regions of the world, including North America, taking a considerable toll on wild birds and mammals,” observes ProMED zoonotic diseases moderator Pablo Beldomenico.
“Infections by HPAI viruses in mammals were typically not common, but since April 2022 there have been a growing number of events of HPAI H5N1 infections in mammals,” Beldomenico told ProMED members on June 6, 2024.
“Moreover, there is convincing evidence of mammal-to-mammal transmission,” Beldomenico assessed. “A recent report showed that HPAI H5N1 infecting elephant seals and sea lions in Argentina have a genomic composition that strongly suggests an evolution into a separate marine mammal clade, supporting mammal-to-mammal transmission.
“Also,” Beldomenico noted, “the dynamics of infection in cattle farms of the USA strongly supports cow-to-cow transmission.”
(Beth Clifton photo)
Cat-and-mouse
The USDA Animal & Plant Health Inspection Service on June 4, 2024 reported H5N1 detections in house mice, collected from Roosevelt County, New Mexico between May 6 and May 12 “from a location where highly pathogenic avian flu had been detected in poultry.”
Forty-seven infected mice were found by June 11, 2024.
Not surprisingly, in view of both the cat-and-mouse relationship and the cat-and-bird relationship, the USDA Animal & Plant Health Inspection Service also reported finding 21 H5N1-infected domestic cats, in locations including Harmon County, Oklahoma; Clinton County, Michigan; Jerome County, Idaho; and Morgan County, Colorado.
(Beth Clifton collage)
Mouse-to-mouse transmission “would be of great concern”
“More and more wild and domestic animals are testing positive for this particular strain of the avian influenza virus,” mused Tam Garland, retired head of the toxicology section at the Texas A&M Veterinary Medical Diagnostic Laboratory
“Are we becoming saturated with this strain, so it is spreading to other animals,” Garland asked, “or are we better at testing for it in mammals and looking for sick animals?
“I suppose the answer could go either way,” Garland said, “as we may not have been looking for H5N1 in many mammal species in previous outbreaks as frequently as we are now.”
Agreed Beldomenico, “There is a need for more studies to confirm mouse-to-mouse transmission of HPAI H5N1 in the house mouse. If this is confirmed, the situation would be of great concern as house mice are a synanthropic species in close contact with humans.”
Merritt & Beth Clifton with Henry the rooster.
“Synanthropic” means “ecologically associated with,” the same concept that appears increasingly likely to apply to humans and farmed animals.
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