When bird flu first struck dairy cattle a year ago, it seemed possible that it might affect a few isolated herds and disappear as quickly as it appeared.
Instead, the virus infected more than 900 herds and dozens of people, killing one person, and showed no signs of an outbreak.
More than a dozen experts said in interviews that a human pandemic is not inevitable yet. But a series of developments over the past few weeks indicate that this possibility is no longer far-fetched.
Useless guidelines, inadequate testing and long delays in publishing data – echoes of mistakes made during the Covid-19 pandemic – squandered opportunities to contain the outbreak, experts said.
In one example of the chaos, a small number of Idaho dairy herds that were infected with bird flu in the spring developed mild symptoms for a second time in late fall, The New York Times has learned.
In mid-January, the Agriculture Department said no new infections had been detected in Idaho herds since October. But state officials Milder cases were discussed publicly in November.
Experts said that a second bout of infection that could lead to milder symptoms in livestock is not surprising, and could be good news for farmers.
But reinfections suggest that the virus, called H5N1, could circulate on farms indefinitely, finding opportunities to evolve into a more dangerous form — a “high-risk” scenario, said Louise Moncla, an evolutionary biologist at the University of Pennsylvania.
“You could easily end up infected with the H5 virus that is endemic in dairy herds without developing symptoms, obscuring rapid or easy detection,” Dr. Moncla said.
She and other scientists said it is impossible to predict if the virus will develop the ability to spread between people, let alone when. But what worries them is that if bird flu finds the right combination of genetic mutations, the outbreak could escalate quickly.
“I’m still not worried about packing up and heading for the hills, but there have been more signs over the last four to six weeks that this virus has the potential” to cause a pandemic, Richard said. Webby, an influenza expert at St. Jude Children’s Research Hospital.
Federal officials have also subtly changed their tone in discussing the outbreak, now emphasizing how quickly the situation could change.
For the general public, H5N1 “presents a low risk, compared to other risks they face today,” said Dr. Nirav Shah, principal deputy director of the Centers for Disease Control and Prevention. “But this can change 100%,” he added. “This is a dangerous virus.”
Health experts stress that there are precautions Americans can take. Do not touch sick or dead birds or other animals; Get tested if you have flu-like symptoms; Do not consume raw milk or meat, or feed them to your pets.
If a larger outbreak occurs, the federal stockpile contains a few million doses of bird flu vaccine. But the vaccine may need to be updated to match the evolving form of the virus. Either way, officials will have to scramble to produce enough for the population at large.
The CDC recommends Treatment with the antiviral drug TamifluBut studies have shown that this medicine It does very little To relieve disease.
Underscoring concerns among many experts, Robert F. Kennedy Jr., who would lead the federal Department of Health and Human Services if confirmed, has been an outspoken critic of Covid vaccines and He said Bird flu vaccines ‘look dangerous’.
Even if a second Trump administration embraces vaccine development, as the first did when Covid struck, it is unclear how many Americans will roll up their sleeves to receive doses.
Influenza usually affects children and the elderly, and sometimes pandemic influenza affects younger people more. But the mistrust created during Covid-19 may lead Americans to avoid precautions, at least initially.
Sophisticated threat
Unlike the coronavirus, which caused chaos with its sudden arrival, influenza viruses typically start in specific animal species or in specific geographic areas.
When a variant of the H5N1 virus emerged in East Asia nearly three decades ago, it mostly sickened birds. In the years that followed, the disease infected at least 940 people, almost all of whom had close, sustained contact with infected birds; Nearly half of these people died.
But since January 2022, when the virus discoverer This has affected wild waterfowl in the United States More than 136 million Commercial, backyard and wild birds, helping to send Egg prices rise.
It also struck dozens of mammal species, including wild and domesticated cats, raccoons, bears, and sea lions.
For at least a year, the H5N1 virus has been infecting dairy cows, which were not known to be susceptible to this type of flu. In some cows, it had lasting effects, reducing milk production and increasing the risk of infection Spontaneous abortion.
In 2024, the virus infected 67 Americans, compared to just one in previous years, in 2022. The sources of these infections are not all known; It is possible that one person may have transmitted the virus to a loved one.
Many of these developments are classic steps toward a pandemic, said Dr. James Lawler, director of the Global Center for Health Security at the University of Nebraska. But he noted, “Where this was supposed to trigger accelerated and expanded action at the federal, state and local levels, we kind of looked the other way as each significant event passed.”
Infections in dairy herds, which first appeared in Texas, appear to have begun to decline last summer. But in late August, California announced its first case. The state’s numbers quickly rose sharply, prompting Gov. Gavin Newsom to do so Declaring a public health emergency In December.
“That was a signal to me, like, ‘OK, this isn’t going away,’” said Dr. Manisha Jothani, commissioner of the Connecticut Department of Public Health.
“Over the past couple of months, I’ve felt like the rhythm has increased,” she said.
Several other recent events have raised the level of concern among experts. In early December, scientists reported that in a laboratory setting, One mutation It helped the virus infect human cells more efficiently.
Late last year, two people, a 13-year-old Canadian girl and a Louisiana resident over 65, became seriously ill with bird flu. Previously, most people infected with H5N1 in the current outbreak did not have severe symptoms.
The Louisiana patient, who had underlying health conditions and was caring for sick and dying birds, He died in early January.
It was the girl Put on life support due to organ failure, but he eventually recovered. Scientists still do not know how it became infected; Her only risk factor was obesity.
Both patients were infected with a new version of the virus that differs from that found in dairy cows and is now widespread in birds. In both people, the virus acquired mutations during infection, which may allow it to infect people better.
“It is clear that we are now receiving new viruses forming in the wild bird reservoir,” Dr. Moncla said. “It has become difficult to control all the different threats.”
Some experts find it particularly concerning that the virus appears to be present in food sources such as raw milk Raw pet food. Domesticated Cats He owns He died In many states, Urging recall For at least one brand of pet food and new federal guidelines on it Quality pet food.
“I think the issue of raw pet food is very concerning,” said Dr. Jane Marrazzo, director of the National Institute of Allergy and Infectious Diseases.
Pasteurization kills the live virus, as does cooking meat at high temperatures. However, neither procedure is perfect, as Dr. Marrazzo noted: “There is no way that you can monitor production and sterilization in a way that guarantees that the food supply will be 100 percent safe.”
Defective response
In the year since the outbreak began, federal officials have announced other measures to prevent or prepare for the pandemic. But experts say each has significant drawbacks.
The Department of Agriculture has been slow to start testing H5N1 vaccines on cows, leaving interested companies in limbo. Dr. Marrazzo said the department had published genetic information from virus samples but did not say where or when they were collected — details that would help scientists track the virus’s evolution.
It is also unclear how many herds have become infected again or have been battling infections for months. In Idaho, some herds infected in the spring appeared to recover but showed milder symptoms again in November.
“From the data we have so far, we do not see evidence of new infections or reinfections in previously infected herds, but rather a failure to clear the original infection,” a USDA spokesperson said in an email response.
But outside experts said the course of symptoms indicated a second round of the disease.
USDA program To test bulk milk It began in December — nearly a year after the outbreak began — and still does not include Idaho. Involving outside companies may help the program move faster.
Ginkgo Bioworks, a company that has worked with federal agencies during the Covid pandemic, already works with a partner that is evaluating nearly half of the nation’s commercial milk supply for bacteria, antibiotics and other substances.
Adding H5N1 to the list would be straightforward, so “why not add testing to this infrastructure we already have?” Matt McKnight, the company’s director of biosecurity, said:
Earlier this month, the Biden administration announced Announce $306 million in new funding, about a third of it for monitoring, testing and outreach to farmworkers.
But farmworkers in some places like the Texas Panhandle still don’t understand what avian flu is, how it spreads and why it should concern them, said Bethany Alcotter, director of research and public health programs at the National Center for Farmworker Health.
As a result, she added, many workers are still not using protective equipment, including in milk shops where the virus is believed to be spreading.
Human testing has been voluntary, and there have been cases of infection It’s been missed. A small number of farmworkers have chosen to get tested, fearing immigration officials or employers.
“If you don’t look for it, you won’t find it, right?” said Dr. Deborah Birx, who served as White House coronavirus response coordinator under President Trump.
“It’s not about lockdowns or activity restrictions. It’s about protecting the American individual by empowering them with information.
