As the virus spreads, so does pessimism about stopping the spread

Bird Flu Snapshot: This is the latest installment in a series of regular updates on the H5N1 flu outbreak in dairy cows that STAT publishes on Monday morning. To read future updates, you can also subscribe to STATs Morning newsletter.

Human cases of H5N1 bird flu infection are on the rise, and another state has joined the list of countries with infected herds of dairy cows.

Colorado announced on Sunday evening that five workers involved in culling chickens at an H5N1-infected poultry farm had tested positive for the virus. Four of the cases have been confirmed by the Centers for Disease Control and Prevention; the fifth is currently considered “presumptive” positive because the individual’s test sample has not yet reached the CDC. All five had mild symptoms: conjunctivitis and mild respiratory complaints. None required hospitalization.

Additional testing by the CDC is needed to fully characterize the viruses responsible for these infections. But assuming they are the same as those circulating in cows (which have occasionally spread to poultry farms), these cases will bring to nine the number of human infections recorded since this outbreak was first discovered in late March. The CDC, at the state’s request, is helping investigate the new human cases in Colorado.

And on Friday came news that another state had discovered a flock infected with bird flu. Oklahoma announced that a sample collected in April and only recently tested turned out to be positive. No explanation was given for the remarkably slow turnaround time in testing the sample. Oklahoma called itself the 13th state to detect H5N1 in dairy cattle, but in reality its ranking should be lower as several states only discovered positive herds in May and June.

These new developments in humans and animals support a blunt risk assessment from the Norwegian Institute of Public Health, which in a recent report gave voice to a growing sense of pessimism about the prospects for containing the H5N1 outbreak in cows.

“There are no clear signs that the outbreak is under control or on the verge of being controlled,” the 26-page document states on the public health risks associated with the ongoing spread.

“The risk that the situation will not be brought under control quickly is high,” the report continues, adding that “the likelihood of… and continued chains of infection is considered high.”

In terms of the impact of continued spread, the report suggests that while the risk posed to humans by the virus is not currently high, it could increase if transmission through livestock continues.

“There is a small but increasing chance that viruses will evolve the ability to effectively infect between and between people,” the report says. “The likelihood increases with prevalence in animals and with the duration of persistent infection from animal to animal.”

The risk assessmentdated June 24, is quickly converted into English by Google Translate for non-Norwegian readers.

It reflects what appears to be a growing view, certainly abroad but probably also in the US, that H5N1 is in no hurry to give up its new hosts and that nothing farmers or government agencies do seems to hasten its departure. . (There’s also a fair amount of skepticism about how farmers or the agency leading the response, the U.S. Department of Agriculture, are working toward that goal.)

Michigan, which has been the model state in terms of its efforts to find and report affected herds and earn the trust of alert farmers, had gone nearly a month without reporting a new infected herd. On July 5, it announced a flock in Gratiot County that has suffered outbreaks in both poultry and dairy cattle since early May. Texas has not added to the list of affected herds in three weeks. That changed on July 8.

As of Friday, the USDA had listed 152 herds in 12 states that had tested positive for H5N1 since the outbreak was first confirmed in late March. Oklahoma adds one to each of these numbers.

While the number of affected herds has steadily risen in some of the reporting states – think Michigan, Colorado, Idaho – the number of states with a dairy industry that have not reported any outbreaks is a mystery to experts monitoring the situation. (Some are downright dubious.) California, Wisconsin, New York, Pennsylvania and Washington rank in the top 10 dairy-producing states by sales. None of these five have reported an affected herd.

Are they luckier? More vigilant? Do cows move less often in those states? We don’t have those answers yet. But a news report from Missouri last week may help explain a possible difference between reporting and non-reporting states. (Missouri is one of the latter.)

Reporter Mary McCue Bell in Columbia-Missouri quoted a veterinarian with the Missouri Department of Agriculture’s animal health division as saying that only 17 dairy cows — in a state with 60,000 cows — have been tested for H5N1 so far.

There is a maxim in epidemiology: Seek and you shall find. It seems some states aren’t looking.

The lack of a clear picture of how widespread the outbreak is in cattle continues to hamper efforts to assess whether this outbreak can be stopped and how best to do so when that goal is within reach.

When asked Thursday whether they thought the virus could be eradicated from dairy cattle at this point, senior leaders at the World Health Organization (WHO) hedged their bets. Maria Van Kerkhove, acting director of the WHO’s Division for Epidemic and Pandemic Preparedness and Prevention, said too little is currently known about the outbreak to make a prediction one way or another.

“I think that is a complicated question,” Van Kerkhove said during a WHO press conference. “That doesn’t mean it couldn’t happen. But I think that before we can get an answer to the question of whether and when that might be possible, we first need to understand to what extent [of spread].”

And Mike Ryan, head of the Public Health Emergency Program, said the continued presence of the virus in wild birds will continue to complicate efforts to control the spread of H5N1 among domestic animals. It’s not just a matter of getting rid of it, the goal should be to keep it out of an animal population – whether that’s poultry or dairy cattle. And that will require resources, oversight and long-term commitment from the veterinary, conservation and public health sectors, he said.

“And unfortunately in the world where we are looking for silver bullets and the treatment that will cure everything, unfortunately the treatment for most of our ills as a human civilization is collaboration, policy, resources and the will to do the work,” Ryan said.

Since USDA confirmed the presence of the virus in dairy cattle on March 25, there have been four confirmed and three suspected human infections, all among farmworkers. All individuals had mild symptoms; some had only conjunctivitis, while a few had respiratory symptoms similar to those seen with infection with human influenza viruses.

The announcement of the fourth case, on the eve of the July 4 holiday, led Adam Kucharski, co-director of the Center for Epidemic Preparedness & Response, at the London School of Hygiene and Tropical Medicine, tosk on the social platform X: “What’s the plan?”

Kucharski put forward a number of hypotheses: What if there are clusters of cases? Cases among people who have had no contact with cows? Suitcases exported to other countries? – to drive home the point that just four years after the start of the worst pandemic since the 1918 Spanish flu, the world does not seem to be grappling with the fact that the spread of the H5 virus in cows could lead to the spread of the H5 virus in humans.

“What is the plan here in 2024 to deal with an outbreak of a potentially pandemic pathogen like H5N1?” he asked.