The H5N1 strain of bird flu responsible for the deaths of tens of millions of birds in the United States in recent months, and countless others around the world, poses an existential threat to the poultry industry in the United States and a potentially widespread threat to human health, experts say. .
The strain, first identified in domestic waterfowl in China in 1996, is responsible for nearly 58 million bird deaths in the United States in the past year. According to the US Centers for Disease Control and Prevention, these deaths have occurred both directly from the virus and indirectly, when herds are slaughtered to limit their exposure. The virus has an almost 100% mortality rate in birds, killing most infected people within 48 hours.
This season’s bird flu outbreak is the worst in US history, having surpassed a 2015 outbreak that the CDC once called “arguably the most significant animal health event in the world.” history of the United States”. That year, nearly 51 million birds died nationwide from H5N1 and related avian influenza viruses. This season’s outbreak is also the worst in UK history, with English farmers ordered to keep their birds indoors from November 7 in a kind of poultry ‘lockdown’ .
The so-called “R zero” value – or the number of people infected by a single infected person, on average – for COVID initially ranged from 1.5 to 7, and now sits at more than 12.
The zero R-value of H5N1 in birds: “around 100,” according to Chowdhury.
It’s an environmental crisis that’s already affecting humans, driving up the price of poultry and making eggs harder to find. US egg retail costs have doubled over the past year and ready-to-cook chicken prices have risen by a quarter or more in the UK, Bloomberg reported recently.
“The world is facing an unprecedented pandemic of bird flu among caged and wild bird populations,” said Rajiv Chowdhury, senior epidemiologist and professor of global health at Florida International University. Fortune.
Additionally, the poultry industry probably cannot “sustain itself in countries like the United States if we continue to see annual surges,” adds Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy ( CIDRAP) from the University of Minnesota..
Economic and food supply issues aside, the pressure has also made people sick, although in small numbers so far. But the trend towards minimal transmission between humans may not hold, 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 of no apparent cause.
Oserholm and Chowdhury worry about further spread from birds to humans and possible transmission from humans who contract bird flu to other humans, especially as the virus crosses the globe and makes the leap to more mammals. , due to mutations.
Last week, the first grizzly bears to be documented with highly pathogenic avian flu were euthanized in Montana after being found partially blind and disoriented, along with other neurological issues. Foxes, dolphins, possums, skunks, seals, other types of bears and a bottlenose dolphin are among other species infected since last year, according to the US 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 lasting way, it could shake the world in a way not seen since the Spanish flu of 1918.
If H5N1 does indeed make a lasting crossbreed with humans, “the potential impact could be significant”, he says, signifying the start of a “new global influenza pandemic”.
“Unusual” in humans, but very deadly
The Ecuadorian victim of the virus – the first in the country, as well as the first in the Latin America/Caribbean region – was admitted to hospital with symptoms of nausea, vomiting and constipation on December 30, where she was presumably being treated for meningitis, according to a January 18 WHO disease outbreak update.
On January 3, she was taken to a pediatric hospital in critical condition after suffering septic shock and being diagnosed with pneumonia. She tested positive for the H5N1 strain on January 7 and remained hospitalized, sedated and on a ventilator from January 17, the international health organization said.
The previously healthy girl becomes the seventh person sickened by the virus since 2020, according to the World Health Organization. While H5N1 is considered highly infectious, it’s only in birds. It is generally difficult for the virus to make the leap to humans, and human-to-human transmission is “unusual”, according to the International Health Organization.
However, when the virus makes the jump, it is very deadly, with a fatality rate of over 50% in humans, according to the CDC.
H5N1 epidemics have followed each other throughout a quarter of a century, without sustained transmission in humans, Osterholm points out. Hundreds of human cases were identified in Egypt at the start of this century, although there was no sustained human-to-human transmission. The toll of the virus gives hope that transmission to humans, and among them, will remain the exception rather than the rule.
Chowdhury says the 1918 flu pandemic serves as a cautionary tale, however. Like the H5N1 flu, the Spanish flu is thought to be of bird origin. Both viruses contain genes that allow them to replicate efficiently in human bronchial cells, according to a 2006 report from the Washington, DC-based Population Reference Bureau.
In the case of H5N1 in humans, such inflammation can lead to “intense inflammation” of lung cells, much more so than would be seen in a typical flu. A similar effect was noted in Spanish flu victims, whose autopsies revealed “lungs choked with debris from excessive inflammation”, leading to drowning, the report notes.
While seasonal flu symptoms include fever, cough, sore throat, runny nose, body aches and fatigue, according to the CDC, H5N1 symptoms in humans are usually much more severe. According to the WHO, they include an often high fever, weakness, cough, sore throat and muscle aches, abdominal pain, chest pain, and diarrhea. These symptoms can quickly give way to breathing difficulties, pneumonia and/or acute respiratory distress syndrome, which is often fatal, as well as neurological effects such as seizures.
The seasonal flu vaccine does not cover H5N1, according to the WHO. And while candidate vaccines against the viral strain have been developed, “they are not ready for widespread use”, according to the organization.
When it comes to planning for the next pandemic, the flu has always been considered a likely culprit, says Dr. Georges Benjamin, executive director of the American Public Health Association. Fortune.
While the Ecuadorian girl and her worrying battle with H5N1 “could very well be a unique case,” “we could easily have an H5N1 or another flu pandemic,” he says.
“That should scare you.”
Although there is currently no reason to suspect sustained transmission of H5N1 among humans, the outlook may not be as bright for the US poultry industry, which is in “deep trouble right now.” Osterholm said. Fortune.
“They need to change biosecurity procedures,” he says, adding that the virus cannot be kept out of herds just by “putting up a screen” because it is airborne.
“These barns are going to require a lot more air handling considerations,” he adds. “H5N1 fundamentally rewrote avian flu.”