FThere are growing doubts about whether the US can exercise control the outbreak of bird flu Among dairy cattle, federal officials reiterated Tuesday that they believe the country can still eliminate the H5N1 virus from dairy cows even as it continues to spread to new herds.
“All the signs we have are that with good biosecurity and good farmer participation, we can eliminate this,” Eric Deeble, acting senior adviser for the H5N1 response at the U.S. Department of Agriculture, said on a call with reporters .
The reason for this confidence, according to Deeble, is that research has shown that the transport of cows and the shared use of equipment and vehicles cause the spread of the virus. That means cutting off the virus at those points can contain it, he said, noting that officials have seen no new introductions of the virus from birds to dairy cows since the outbreak began, likely late last year.
“We understand this affects livestock and the people closely associated with them, so improved biosecurity should get us to a point where we can stop the spread,” Deeble said. He added that the possible future use of an H5 vaccine in cattle – an idea still under discussion – “could further facilitate the elimination of this disease from the national herd.”
External experts are becoming increasingly skeptical from that point of view, given the terrain in which the virus continues to gain ground. They have argued that the problems that have hampered the response to the outbreak from the start — from a surveillance system that fails to track the spread of the virus to a lack of cooperation from dairy farms — have not changed dramatically. And they argue that the longer the virus persists in livestock, the more likely it is that it could mutate in a way that makes it more transmissible between people.
The USDA has begun providing more resources to farms with infected cows, which could increase dairy farms’ willingness to test their animals. But experts still believe that poor tracking of the virus — officially more than 155 herds in 13 states have reported infections, though both figures are widely believed to be too low — means officials are not measuring the size of the outbreak or all herds know. that are affected. Studies have also found that farmers have continued to move cows even after they showed signs of illness.
“There are no clear signs that the outbreak is under control or on the verge of coming under control,” a report from the Norwegian Institute of Public Health said last month, adding that “the likelihood of… sustained chains of infection is considered high.”
Deeble’s comments came as health and agriculture officials provided an update on a cluster of human H5N1 cases in Colorado.
The five cases (four confirmed, one still considered suspected) involved people involved in culling birds at a poultry farm with an H5N1 outbreak in Weld County, Colorado. But available evidence suggests the virus may have reached the 1.8 million bird farm through an infected dairy herd.
During the press call, officials noted that there have been infected dairy herds in Weld County. They also said a genetic sequence from one of the human cases indicated the virus was related to the version spreading among cows. Notably, the genetic sequence of a key component of the virus — the hemagglutinin subunit — matched exactly the hemagglutinin sequences of two previous human cases linked to the dairy outbreak, officials said.
“That raises the possibility that this virus was transmitted from a dairy herd in Colorado to the poultry farm,” Nirav Shah, the deputy director of the Centers for Disease Control and Prevention, told reporters. “That’s a hypothesis. It is a hypothesis that needs and requires a full investigation. But that is a hypothesis at the moment.”
The five cases in Colorado were all mild, Shah said. The people had varying symptoms, with some experiencing the more traditional flu symptoms of fever and coughing, and others having conjunctivitis, a symptom that has been seen in some dairy workers who became infected during the outbreak.
The human cases also underscored some of the challenges authorities face in preventing spread from animals to people. Health officials have urged dairy workers to wear personal protective equipment in milking parlors, for example, given skyrocketing virus levels in cows’ udders and their milk. But parlors can be hot and stuffy, meaning it’s not comfortable or feasible to wear masks and goggles.
Workers involved in culling poultry with H5N1 outbreaks — “depopulation” in the parlance of agriculture officials — are scheduled to wear full PPE, from boots to suits to masks and goggles. But officials noted that when the cull took place, it was more than 100 degrees in Colorado. In addition, the industrial fans intended to cool the sheds where the slaughter took place were so strong that it was difficult for workers to keep their masks and goggles on their faces. In addition, the fans were busy fluffing bird feathers, which can transmit the virus.
The culling method used on this farm — which requires workers to pick up chickens and place them in a cart where they are euthanized with carbon dioxide — also meant there was a lot of contact with the birds, officials said.
“We understand that the use of personal protective equipment was suboptimal, especially the masks and eye protection,” Shah said. However, he added that “these factors highlight a path to prevention,” with better technique and PPE use potentially preventing future cases.