overview
- This year, the bird flu epidemic has led to several alarming developments, with at least 64 human infections.
- Experts outlined several indicators that the spread of the virus is moving in the wrong direction.
- These include the recent detection of the virus in wastewater and signs of dangerous mutations.
The smoldering threat of bird flu may be slowly coming to a boil.
This year has been marked by a series of alarming developments regarding the spread of the virus. At least 64 people have tested positive for the virus since April, making it the first case in the U.S. except for one in 2022. Dairy herds in 16 states were infected this year. The Centers for Disease Control and Prevention on Wednesday confirmed the nation’s first severe case of avian influenza in a critically ill patient in Louisiana. California Governor Gavin Newsom declared: State of emergency declared this week in response to growing outbreak in cattle and poultry.
“The traffic lights are turning from green to yellow,” said Dr. Peter Chin-Hong, a professor of medicine at the University of California, San Francisco, who studies infectious diseases. “So many signs are pointing in the wrong direction.”
No human-to-human transmission of avian influenza has been recorded, and the CDC maintains that the immediate risk to public health is low. But scientists are growing concerned based on four key signs.
As one example, the avian influenza virus known as H5N1 is spreading uncontrollably among animals, including cattle, that frequently come into contact with humans. Furthermore, detections in wastewater indicate that the virus has left its mark not only in livestock but also in a wide range of areas.
In addition, there are some human cases where the source of infection has not been identified, and there are studies on the evolution of the pathogen, suggesting that the virus has evolved to better fit the human receptors needed to spread between people. It has been shown that there are fewer mutations.
Experts say these indicators taken together suggest the virus is on its way to becoming the next pandemic.
“We’re in a very precarious situation right now,” says Scott Hensley, a professor of microbiology at the University of Pennsylvania.
Extensive circulation creates new routes to people
Since this avian influenza outbreak began in 2022, the virus has spread to wild birds, domestic poultry, and wild mammals such as sea lions, foxes, and black bears. more 125 million poultry died from infectious diseases or were culled In the United States, according to the U.S. Department of Agriculture.
In March, an unwelcome surprise occurred when the dairy cows became ill, their feed intake decreased, and the milk began to discolor.
The virus likely spread quickly and efficiently between cows through raw milk, as infected cows shed large amounts of virus from their mammary glands, according to the study. Raccoons and domestic cats also seem to get sick if they drink raw milk.
The more animals that become infected, the greater the risk of infection for humans who come into contact with them.
“The more people are infected, the more likely it is that variants will emerge,” said Jennifer Nuzzo, a professor of epidemiology and director of the Pandemic Center at Brown University’s School of Public Health. “I don’t like giving the virus a runway into a pandemic.”
Until this year, cows had not been the focus of influenza prevention efforts.
“We didn’t think dairy cows were hosts for influenza, at least not meaningful hosts,” Andrew Bowman, a professor of veterinary preventive medicine at The Ohio State University, told NBC News this summer.
But the virus has now been detected in at least 865 herds in at least 16 states and in raw (unpasteurized) milk sold in California. For domestic cats who drink raw milk.
“Right now, it is raw milk and cheese products that are directly putting communities and consumers at risk,” Chin-Hong said. “A year ago, or even a few months ago, the risk was much lower.”
Cases where the source of exposure is unknown
The majority of human H5N1 infections occur among poultry and dairy farm workers. However, in some mysterious cases, the source of infection has not been identified.
The first one is Missouri inpatients He tested positive in August but has since recovered. The other is California children reported infected in November.
Additionally, Delaware health officials reported a case of H5N1 infection this week in a person with no known exposure to poultry or cattle. However, because CDC testing did not confirm that the virus was avian influenza, the agency considers this a “probable” case.
In Canada, a British Columbia teenager was hospitalized in early November after contracting H5N1, although he had no known contact with farm animals or wild animals. The virus’ genetic material suggested it was similar to strains circulating in waterfowl and poultry.
Unexplained cases like this are giving some experts pause.
“This suggests that this virus is much more widespread and that more people may be exposed to it than previously thought,” Nuzzo said.
Increased concentration of avian influenza in wastewater
To better understand the geography of the avian influenza epidemic, scientists are monitoring wastewater for fragments of the virus.
Amy Lockwood, director of public health partnerships at the CDC and Verily, a company that provides wastewater testing services to the CDC, said that in recent months, “we’re seeing detections in more places and they’re happening more frequently.” “It was,” he said. A program called Wastewater SCAN.
Earlier this month, about 19% of facilities covered by the CDC’s National Wastewater Surveillance System across at least 10 states. Positive detection reported.
It is impossible to know whether the virus fragments found came from animals or humans. For example, some may come from wild bird waste that flows into storm drains.
“At this point, we don’t think these are indicative of human-to-human transmission, but there are a lot of H5 viruses out there,” said Peggy, Director of Infectious Disease Control and Innovation.・Mr. Honein stated. CDC.
Lockwood and Honein say wastewater detections occur primarily near dairy processing sites and poultry farms, but in recent months mysterious hotspots have emerged in areas without such agricultural facilities. He said it is emerging.
“We’re starting to see infections in places where we don’t automatically know what the source is,” Lockwood said, adding: “We’re in a huge numbers game.”
One more mutation?
Until recently, scientists who study virus evolution thought that several mutations were necessary for H5N1 to spread easily among humans.
But please research Published in Science magazine This month it was discovered that a version of the virus circulating in cattle could bind to human receptors after a single mutation. (The researchers are only studying the viral proteins, not the complete infectious virus.)
“We don’t want to think that a pandemic is more likely because of this finding. We just want to point out that the risk increases as a result of this,” said Co-author of the study, Scripps Research. said Jim Paulson, director of molecular medicine at .
Separately, scientists have identified worrying elements in another version of the virus found in a Canadian teenager who became seriously ill in recent months. Hensley said virus samples show evidence of mutations that could make it more spreadable between people.
A CDC spokesperson said it is unlikely that the virus had these mutations at the time the boy was infected.
“This mixed change in the virus most likely occurred after a long-term infection in the patient,” the spokesperson said.
The agency’s research does not suggest that “the virus is adapted to be easily transmitted between humans,” the spokesperson added.
The strain of the virus in the first severe case of bird flu in the United States, announced Wednesday, was the same strain that infected a Canadian teenager.
Dr. Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases, said the CDC is evaluating samples taken from the patient to determine whether variants of concern are present.
Meanwhile, Hensley said he is concerned that flu season could be a fast track for the virus to evolve. If someone is co-infected with a seasonal influenza virus and avian influenza, the two can exchange chunks of genetic code.
“There’s no need for mutations, just genes being replaced,” Hensley said, adding that he wants farmworkers to get flu shots to limit such opportunities.
Upcoming tests and vaccines
Experts said there is much that can be done to better track the spread of bird flu and prepare for a potential pandemic. Some of that work has already begun.
The USDA expanded mass testing of milk to a total of 13 states on Tuesday. Accounts for approximately 50% of the national supply.
Nuzzo said efforts cannot be ramped up right away.
“We have waited too long to conduct extensive bulk milk testing, which is how we find most outbreaks on farms,” she said.
At the same time, Verily’s chief medical and scientific officer, Andrew Trister, said the company is working to improve wastewater analysis in hopes of identifying relevant mutations.
USDA also Approves field trial of vaccination of cattle against H5N1. Hensley said his lab tested a new mRNA vaccine in calves.
The federal government has two types of avian influenza vaccines in stock for human use, but their use must be approved by the Food and Drug Administration.
Nuzzo said health officials should offer vaccines to farm workers.
“We shouldn’t wait for farmworkers to die before acting,” she says.
Additionally, scientists are developing new mRNA vaccines against H5N1. This type of vaccine, first used against Covid-19, can be more quickly tailored to specific virus strains and can also be scaled up more quickly.
Hensley Lab in May reported that an mRNA vaccine candidate provided protection against the virus in ferrets during preclinical testing.. Another candidate being developed by the CDC and Moderna is also showed promising results Ferrets are often used as a human model to study influenza.
“All that’s left is to do the clinical trials,” Hensley said.
correction (December 22, 2024, 5:10 p.m. ET): A photo caption in a previous version of this article incorrectly stated when the Department of Agriculture ordered an inspection of the nation’s milk supply. It was December 6th, not last week.
