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PIRBRIGHT, United Kingdom — In a startling revelation, scientists warn that the current global strategies to control bird flu are failing, potentially paving the way for another human pandemic. A comprehensive review led by The Pirbright Institute has uncovered alarming evidence that the H5N1 bird flu virus is finding new ways to spread among mammals, raising concerns about its ability to jump to humans.
Dr. Thomas Peacock, a zoonotic influenza specialist leading the study published in Nature, says the findings, which are still awaiting further peer review, paint a worrying picture.
“Influenza A viruses have caused more documented global pandemics in human history than any other pathogen,” Dr. Peacock explains in a media release.
While pigs have traditionally been seen as the stepping stone for avian flu to adapt to mammals before infecting humans, the landscape is changing. Recent studies have documented the spread of bird flu to cows, cats, and other animals.
“The altered ecology of H5N1 has opened the door to new evolutionary pathways,” Dr. Peacock warns.
What does this mean for humans?
Bird flu, or avian influenza, is a virus that primarily affects birds. However, in recent years, it’s been making headlines for infecting an increasing number of mammals, including seals, minks, and even cattle. This shift is causing scientists to sit up and take notice, as it suggests the virus is becoming more adept at crossing species barriers.
The new review highlights several red flags that suggest our current defenses against a potential bird flu pandemic in humans are woefully inadequate. For instance, in the United States, researchers say there’s a reluctance to embrace modern vaccine technologies and improve surveillance methods. Even more concerning is the lack of data collection on H5N1 transmission between cows and humans on U.S. dairy farms.
“H5N1 is a reportable disease in poultry, but not mammals, in the US. The US Department of Agriculture requires H5N1 testing only in lactating cattle prior to interstate movement,” Dr. Peacock points out.
This means that the virus could be spreading silently among mammals without our knowledge.
The scientists also raise concerns about how we monitor wildlife for the virus. Current practices focus on testing dead animals rather than living ones, potentially missing early signs of the virus’s spread and evolution.
“What keeps scientists up at night is the possibility of unseen chains of transmission silently spreading through farm worker barracks, swine barns, or developing countries, evolving under the radar because testing criteria are narrow, government authorities are feared, or resources are thin,” the study authors write in their report.
How is the virus managing to spread so effectively?
The answer lies in a process called “genomic reassortment.” Imagine the flu virus as a Lego set with eight blocks. When two different flu viruses infect the same animal, they can swap these blocks, creating a new virus with a mix of traits from both parents. This process is driving the current global outbreak of bird flu.
The review suggests that a reassortment event between two types of bird flu viruses in Europe or Central Asia around 2020 created the current strain that’s infecting South American marine mammals and U.S. dairy cattle. This ability to mix and match genes makes the virus highly adaptable and unpredictable.
So, what can be done to prevent a potential human pandemic? The researchers stress the need for new control strategies, including vaccination. While current flu vaccines for poultry can reduce disease severity, they don’t prevent infection entirely. However, there’s a glimmer of hope: stocks of H5 vaccine related to the current circulating viruses exist and could be rapidly produced using mRNA technology if H5N1 starts spreading in humans.
The good news is that recent human infections with H5N1 have been less severe than previous outbreaks. In past Asian outbreaks, about half of the reported infections were fatal. Current cases in the U.S. have been milder, possibly due to the virus entering through the eyes rather than causing pneumonia in the lungs.
Interestingly, older individuals may have some protection against H5N1 due to childhood exposures to similar viruses. However, younger people born after the 1968 flu pandemic might be more vulnerable to severe illness if H5N1 were to become a human pandemic.
Paper Summary
Methodology
The researchers looked into how the H5N1 influenza virus, typically seen in birds, has started infecting mammals worldwide. They collected virus samples from infected animals such as birds, marine mammals, and even dairy cows, across multiple regions like South America and the U.S. Using these samples, the scientists analyzed the genetic makeup of the viruses to understand how they have evolved and spread between different species. They also observed cases where the virus was able to move from one mammal to another, which hadn’t been seen much before. They tested this using advanced lab techniques and genetic sequencing to track how the virus might adapt to new hosts.
Key Results
The study found that the H5N1 virus, which usually affects birds, is now infecting different mammals like sea lions and dairy cows. In some places, it even spread between these animals. The virus has changed over time, making it easier to jump from birds to mammals and, in some cases, pass between mammals. The study raised concerns because these changes could increase the chances of the virus spreading to humans. Although the virus hasn’t widely affected people yet, there have been a few human cases in South America and the U.S.
Study Limitations
First, the study relies heavily on samples from animals that were already sick or dead, meaning it may miss instances where the virus didn’t cause obvious symptoms. Also, the exact mechanisms for how the virus spreads between mammals, like sea lions or cows, remain unclear. More field data is needed to confirm whether mammals can easily spread the virus to humans. Finally, while some genetic changes in the virus were identified, predicting future mutations remains difficult.
Discussion & Takeaways
This study highlights a significant shift in the behavior of the H5N1 virus, which is expanding its range from birds to mammals. The main concern is that this could lead to a future where the virus spreads among humans, though this hasn’t happened yet. The study also emphasizes the need for improved monitoring and surveillance, especially in mammals that interact closely with humans, such as dairy cows. The virus’s ability to adapt to new species raises questions about whether current control measures, like culling infected animals, will be enough to prevent a future outbreak in humans.
Funding & Disclosures
This study was conducted by a team of researchers from multiple institutions, including Imperial College London, University of Pennsylvania, and the National Institutes of Health (NIH). Funding sources are not fully detailed in this early version of the paper. The authors have disclosed no potential conflicts of interest in the published material. The researchers add that this study will undergo further editing following the publication of these early findings.
