The H5N1 strain of avian flu responsible for the deaths of tens of millions of birds in the US in recent months, and countless more worldwide, poses an existential threat to the US poultry industry – and a potentially widespread threat to human health. health, experts say.
The strain – first identified in domestic waterfowl in China in 1996 – is responsible for nearly 58 million bird deaths in the US in the past year. These deaths have occurred both directly as a result of the virus and indirectly, when flocks are culled to curb further exposure, according to the U.S. Centers for Disease Control and Prevention. The virus has a nearly 100% mortality rate among birds and kills most infected within 48 hours.
This season’s bird flu outbreak is the worst in U.S. history, surpassing a 2015 outbreak that the CDC once called “arguably the most important animal health event in U.S. history.” That year, nearly 51 million birds died nationally due to H5N1 and related avian flu viruses. This season’s outbreak is also the worst in UK history, with farmers in England ordered from November 7 to keep their birds indoors in a sort of poultry “lock-down”.
The so-called “R zero” value – or the number of people infected on average by a single infected person – for COVID initially ranged from 1.5 to 7, and now exceeds 12.
The R-zero value of H5N1 in birds: “around 100,” Chowdhury said.
It’s an environmental crisis that is already affecting people, driving up the price of poultry and making it harder to get eggs. The selling cost of eggs in the US has doubled in the past year and oven-ready chicken prices have risen by a quarter or more in the UK, Bloomberg recently reported.
“The world is facing an unprecedented bird flu pandemic among caged and wild birds,” said Rajiv Chowdhury, senior epidemiologist and professor of global health at Florida International University. Fortune.
In addition, the poultry industry is unlikely to hold up in countries like the US if we continue to see annual increases, adds Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota..
Aside from economic and food supply problems, the tribe has also made people sick, albeit in small numbers so far. But the trend of minimal transmission between people may not last, experts warn. Last week, the WHO reported that a previously healthy Ecuadorian girl had been hospitalized with the virus. How she contracted the virus is uncertain and under investigation, but poultry her family had recently purchased died with no apparent cause.
Oserholm and Chowdhury are concerned about additional spread from birds to humans, and about possible transmission from humans who catch bird flu to other humans, especially as the virus crosses the globe and makes the jump to more mammals, due to mutations.
Last week, the first grizzly bears documented with the highly pathogenic bird flu were euthanized in Montana after they were found partially blind and disoriented, with other neurological problems. Foxes, dolphins, opossums, skunks, seals, other bear species and a bottlenose dolphin are among other species that have been infected since last year, according to the U.S. Department of Agriculture.
The likelihood of human-to-human transmission of H5N1 is “very low,” Chowdhury says. But if it were to happen in a sustained way, it could rock the world in a way not seen since the 1918 Spanish flu.
If H5N1 does indeed make a sustained crossover to humans, “the potential impact could be significant,” he says, signaling the start of a “new global flu pandemic.”
‘Unusual’ in humans, but highly deadly
The Ecuadorian victim of the virus – the first in the country and also the first in the Latin American/Caribbean region – was admitted to a hospital on Dec. 30 for symptoms of nausea, vomiting and constipation, where she was believed to have been treated for meningitis, according to an update on the outbreak from WHO on January 18.
On January 3, she was transported to a children’s hospital in critical condition after suffering septic shock and being diagnosed with pneumonia. She tested positive for the H5N1 strain on Jan. 7 and remained hospitalized as of Jan. 17, under anesthesia and on a ventilator, the international health organization said.
The previously healthy girl becomes the seventh person to become sick with the virus since 2020, according to the World Health Organization. While H5N1 is considered highly contagious, it’s only in birds. It is usually difficult for the virus to make the jump to humans, and human-to-human transmission is “uncommon,” the International Health Organization says.
However, when the virus takes the plunge, it is highly deadly, with a fatality rate of more than 50% in humans, according to the CDC.
H5N1 outbreaks have come and gone for a quarter of a century, with no sustained transmission in humans, Osterholm points out. Hundreds of human cases were identified in Egypt earlier this century, although there was no sustained human-to-human transmission. The track record of the virus gives reason to hope that transmission to humans, and among them, will remain the exception rather than the rule.
However, Chowdhury says the 1918 flu pandemic is a cautionary tale. Like the H5N1 flu, the Spanish flu is believed to have an avian origin. Both viruses contain genes that allow them to efficiently replicate in human bronchial cells, according to a 2006 report from the Washington, D.C.-based Population Reference Bureau.
In the case of H5N1 in humans, such inflammation can cause lung cells to become “severely inflamed”—much more than would be seen with a regular flu. A similar effect was seen in victims of the Spanish flu, whose autopsies revealed that “lungs were suffocated by debris from the excessive inflammation,” resulting in drowning, the report said.
While seasonal flu symptoms include fever, cough, sore throat, runny nose, aches and fatigue, the symptoms of H5N1 in humans are typically much more severe, according to the CDC. They often include high fever, weakness, cough, sore throat and muscle aches, abdominal pain, chest pain and diarrhea, according to the WHO. These symptoms can quickly give way to difficulty breathing, pneumonia and/or Acute Respiratory Distress Syndrome, which is often fatal, as well as neurological effects such as seizures.
According to the WHO, the seasonal flu vaccine does not cover H5N1. And while candidate vaccines for the viral strain have been developed, “they are not yet ready for widespread use,” the organization said.
When it comes to planning for the next pandemic, flu has always been considered a likely culprit, Dr. Georges Benjamin, executive director of the American Public Health Association, tells SELF. Fortune.
While the Ecuadorian girl and her disturbing battle with H5N1 “might be a one-off,” “we could easily get an H5N1 or another flu pandemic,” he says.
“It should scare you.”
While there is currently no reason to suspect continued H5N1 transmission among humans, the outlook may not be as encouraging for the US poultry industry, which is currently in “major trouble,” Osterholm says. Fortune.
“They need to change biosecurity procedures,” he says, adding that the virus can’t be kept away from herds simply by “putting up a screen” because it’s airborne.
“These barns will require a lot more air handling considerations,” he adds. “H5N1 has fundamentally rewritten bird flu.”