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Last April, health officials recorded the second human case of the H5N1 influenza strain in Texas history. Since then, scientists and regulators have acted quickly to contain the potential outbreak. But while research and detection efforts have been frantic, the virus has presented puzzles at every turn.
The first thing that surprised me was the cow.
H5N1, a type of influenza A, has been detected in animals around the world since the 1990s. This virus mainly infects birds such as wild birds and farmed poultry, but nearly 50 species of mammals are also infected.
However, cows are not routinely suspected of H5N1 infection. Not only do they not usually eat birds, but they also don’t usually eat cows. Influenza A host Researchers are still trying to understand why the H5N1 virus is circulating in cattle.
The Department of Agriculture and the Department of Health have been discovering infections since the virus was first detected in dairy cows in Texas last March. in a flock of 46 across nine states. And avian influenza appears to be moving silently through cattle herds. make them sickThis can make tracing virus infections more difficult.
For humans, the effects can be even more dramatic.
of 888 people infected with H5N1 According to the WHO, 463 people have died, more than half of the human infections recorded worldwide since 2003. However, the exact case fatality rate is still unknown, as many milder cases are likely not recorded in that data.
Only two cases have been reported in the United States, including one in 2022, which the CDC suspects resulted from contact with infected birds, but in Texas, a farm worker It is highly likely that the virus was transmitted from birds, making this the first case of infection from a mammal to a human. Cattle – Both had mild symptoms.
The CDC currently The threat of widespread infection to humans is judged to be “low.”
Still, earlier this month, FDA Commissioner Dr. Robert Califf stressed to the Senate Appropriations and Agriculture Committee that there are many reasons to be on high alert and suggested that mortality rates could rise. In humans, it can be as high as 25%. — 10 times worse than COVID-19.
“Like all viruses, this virus mutates,” Khalif said. “We need to continue to prepare for the possibility of jumping to humans.”
While the USDA is tracking outbreaks in animals, CDC officials have set up a dashboard to communicate all information. New cases in humans. The agency also receives data from 600 facilities testing wastewater for the presence of H5N1.
Separately, an academic team from Emory University and Stanford University recently announced the discovery of influenza A in 190 wastewater treatment plants. in 59 locations.
Current spread of infection — in numbers
48
States with current poultry outbreaks.
9
States where cattle are currently affected.
～260
Meanwhile, the FDA is focused on protecting the food supply and developing pharmaceutical response plans for potential human outbreaks.
With all of these efforts in full swing, here are some of the key concerns.
raw milk elements
FDA testing of pasteurized milk revealed genetic traces of H5N1 in 1 out of 5 samples; There is no live virus So far, authorities maintain that milk is generally safe. A bigger concern about the potential for food-to-human transmission of the virus concerns unpasteurized milk.
“Due to the limited information available about the potential for transmission of the H5N1 virus through raw milk, the FDA urges the industry to continues to advise against the manufacture or sale of any product to anyone infected with the avian influenza virus or who has been exposed to a person infected with the avian influenza virus. FDA stated.
Still, raw milk enthusiasts have dismissed these concerns. Weekly sales of raw milk have soared year on year, with social media influencers doubling down on its potential health benefits and stoking anti-government fears. 21% to 65% weekly Since March 25, according to a report by the Associated Press.
In April, USDA stated “We don’t know exactly how the virus moves, but the virus is excreted in milk in high concentrations.”
CDC is long linked Raw milk is susceptible to a variety of foodborne illnesses, including salmonella and E. coli.
Maintaining Regulatory Momentum
Public health experts have derided lawmakers in recent years for failing to pass bills such as: Pandemic and All Hazards Preparedness Actit is likely to maintain momentum in biosecurity.
But when Khalif recently appeared before the Senate Appropriations Committee to introduce FDA’s $7.2 billion budget request for fiscal year 2025 (a $341 million increase over fiscal year 2024), the lawmakers in attendance gave him a warm welcome. He expressed particular interest in maintaining adequate levels of FDA funding for combat. H5N1.
Various agencies are currently involved in the response. As Mr. Khalif pointed out, the USDA regulates cattle, the CDC protects workers, the FDA regulates milk, and is working with HHS on medical countermeasures. But even if lawmakers keep their coffers full, these various branches of government face multiple challenges.
Khalif said in his testimony that government agencies sometimes have difficulty accessing farms for surveillance and detection activities because farmers “by definition” protect the places they work. , he pointed out.
Khalif also said that government agencies often call him to coordinate work, but in a recent report in STAT News, “Turf war” between USDA and FDA This could hinder the government’s response to H5N1.
Khalif said the FDA is also scrambling to prepare for a drug-related response, noting that tests, antivirals and vaccines need to be at the ready.
CDC reported In April, it said: “This virus is very closely related to two existing HPAI A(H5N1) vaccine candidate viruses that are already available to manufacturers and could be used to manufacture vaccines if necessary.” said.
Idiosyncratic behavior of viruses
Scientists around the world are working hard to unravel some of the mysteries surrounding H5N1.
For example, it’s still unclear how exactly the virus infected cattle.
In a recently published study, which has not been peer-reviewed, researchers looked at the multiple entry points cows have for human and avian viruses.Importantly, in this study cows Increased number of bird virus receptors It’s more common in the mammary glands than in other parts of the body, and this may explain why so much virus gets into milk, even though the cows aren’t as sick. However, there was no explanation of how the virus enters the breast. The authors also noted with concern that cows could serve as breeding grounds for the mixing of human and avian viruses, potentially giving rise to new strains of influenza.
Other features of the virus also remain mysterious.
While avian influenza often causes epidemics that then dissipate, H5N1 influenza appears to be spreading. more durable It has been successful in circulating around the world for longer and on a larger scale than other influenza strains.
Scientists also don’t yet know how likely it is to spread from person to person. Dr. Michelle Barry, director of Stanford University’s Center for Global Health Innovation, said in a recent interview that scientists currently lack the data they need for research. Understand sending And in the case of a dairy worker in Texas who contracted the H5N1 virus from a cow, researchers did not perform serological testing.
