Avian Flu Snapshot: This is the latest in a regular series of updates on the H5N1 influenza outbreak in dairy cows that STAT publishes on Monday mornings. You can also subscribe to STAT to read future updates. Morning Round Newsletter.
Cases of H5N1 avian influenza in humans are on the rise, with new states joining the list of infected dairy herds.
Colorado The Department of Health announced over the weekend that five workers involved in culling chickens at a poultry farm infected with the H5N1 virus have tested positive for the virus. Four have been confirmed by the Centers for Disease Control and Prevention, while the fifth is considered a “provisional” positive at this time because test samples have not yet been received by the CDC. All five had mild symptoms, consisting of conjunctivitis and mild respiratory illness. None required hospitalization.
Further testing by CDC required Fully characterize the virus The cause of these infections is unknown, but assuming it is the same virus circulating among cattle (and occasionally infecting poultry farms), these cases bring the number of documented human infections to nine since the outbreak was first identified in late March. CDC is assisting in the investigation of the new human cases in Colorado, at the request of the state.
Then on Friday, news broke that a flock of birds had been found infected with bird flu in another state. Oklahoma State Announces A sample taken in April recently tested positive. The state reported two positive clusters, but this may actually be false.
Lee Benson, a spokesman for the Oklahoma Department of Agriculture and Forestry, said a dairy farm in the state suspected H5N1 virus infection in its cows in April and took swab samples from two barns on its property, but did not submit them for testing at the time. The dairy sent two swabs for testing because the USDA recently launched a compensation program for lost milk production on farms whose cows test positive for avian flu, Benson said.
“I can tell you that the samples that tested positive came from a dairy farm in Oklahoma. They have two barns where they milk their cows and one sample was taken from each barn,” he said.
STAT asked the USDA whether it would change the number of positive herds from Oklahoma, but has not yet responded.
Oklahoma claims to be the 13th state to have H5N1 found in dairy cows, but in reality it is likely lower on the list. Benson said the samples were taken on April 19. At that time, only eight other states had reported positive clusters.
These new developments in humans and animals support a frank risk assessment by the Norwegian Public Health Institute, which in a recent report expressed growing pessimism about the prospects for containing the H5N1 outbreak in cattle.
“There are no clear indications that the spread is or is becoming controlled,” the 26-page document on the public health risks associated with the ongoing outbreak clearly states.
“The risk that the situation will not be brought under control soon is significant,” the report continues, adding that “the probability of … and of sustained chains of infection are considered high.”
As for the impact if the infection continues to spread, the report suggests that the virus currently poses no significant risk to humans, but that this could increase if infection continues in cattle.
“The likelihood that the virus will acquire the ability to transmit effectively to humans and between humans is low but increasing,” the report said. “This likelihood increases with increasing prevalence in animals and the duration of infection between animals.”
Risk assessmentThis article, dated June 24, was quickly translated into English by Google Translate for non-Norwegian readers.
This reflects a growing view abroad, and perhaps even in the United States, that the H5N1 virus is in no hurry to abandon its new host and that nothing farmers or government agencies are doing will hasten its departure. (There is also considerable skepticism about how hard farmers and the U.S. Department of Agriculture, which is leading the response, are working to that end.)
Michigan, an exemplary state in finding and reporting infected herds and winning the trust of vigilant farmers, had not reported any new infected herds for nearly a month. On July 5, the state announced a herd in Gratiot County that had been battling an outbreak in poultry and dairy cattle since early May. Texas was not added to the list of infected herds for three weeks, but that changed on July 8.
As of Monday, the USDA reported that 157 herds in 13 states had tested positive for H5N1 since the first cases were identified in late March.
Among the states reporting cases, Michigan, Colorado and Idaho have seen a steady rise in the number of infected cows, but the number of states with dairy industries that have not reported a single case has left experts monitoring the situation baffled. Highly doubtfulCalifornia, Wisconsin, New York, Pennsylvania and Washington are among the top 10 dairy producing states based on revenue. Five of these states have not reported any affected herds.
Are they luckier? More cautious? Are cattle moving less frequently in these states? The answers are still out there. But a news report from Missouri last week might help explain the difference between reporting and non-reporting states. (Missouri is one of the latter.)
Reporter Mary McKew Bell Columbia Missourian A veterinarian with the Missouri Department of Agriculture’s animal health division said only 17 of the state’s 60,000 dairy cows have been tested for H5N1 so far.
There’s a saying in epidemiology: “Ask and you will find.” It appears some states aren’t asking.
Efforts to assess whether and how best to stop the spread of the infection among cattle remain hampered by a lack of clear knowledge about how widespread the infection is among cattle.
Asked Thursday whether they thought the virus could be rid of dairy cows at this point, senior World Health Organization (WHO) outbreak leaders were cautious about taking any chances. Maria Van Kerkhof, interim director of the WHO’s infectious diseases and pandemic response and prevention department, said there is too little information about the outbreak at this point to predict which way it will go.
“I think it’s a complex question,” Van Kerkhove said at a WHO news conference. “That doesn’t mean it can’t happen, but I think we need to understand the extent of it before we can give an answer as to when or if it could happen. [of spread].”
And Mike Ryan, who heads the World Health Organization’s health emergencies program, said efforts to curb the spread of H5N1 in livestock will remain difficult because the virus continues to be present in wild birds. It’s not just a matter of eradicating the virus; the goal needs to be to eliminate it from animal populations, whether they’re poultry or dairy cattle. That will require resources, surveillance and a long-term effort from veterinarians, wildlife and public health departments, Ryan said.
“And unfortunately, in a world where we’re looking for panaceas and one-size-fits-all cures, the cure for most of our ills as a human civilization is collaboration, policies, resources and the will to do the work,” Ryan said.
Since the USDA confirmed the presence of the virus in dairy cows on March 25, four confirmed and three presumptive cases have been reported, all in farmworkers. All infected people had mild symptoms, some with only conjunctivitis, but several had respiratory symptoms similar to those seen in humans with influenza virus infections.
Following the announcement of the fourth case on the eve of the July 4 holiday, Adam Kucharski, co-director of the Centre for Infectious Disease Control and Response at the London School of Hygiene and Tropical Medicine, said: Ask a question on social platform X: “What’s the plan?”
Kucharski posed a series of hypotheses: what happens if a cluster breaks out? What if the infection spreads among people who have no contact with cows? What if the infection spreads to other countries? He pointed out that just four years after the start of the worst pandemic since the Spanish flu of 1918, the world still doesn’t seem to have come to grips with the fact that the H5 virus, which spreads among cows, can also spread among humans.
“Now in 2024, what is the plan to deal with the outbreak of a potentially pandemic pathogen like H5N1?” he asked.
This article has been updated with new information from Oklahoma.
