A concerning mutation that could lead to widespread human illnesses and potentially even a pandemic, according to some experts, could put the world at risk of human-to-human transmission of the H5N1 bird flu virus, according to California researchers.
A single mutation of the hemagglutinin protein, the H in H5N1, could turn a virus that has so far primarily sickened or killed cows and birds into a pathogen that targets human cells, according to a study published Thursday in the journal Science by scientists at Scripps Research Institute.
The discovery coincides with a state-ordered recall of raw milk products and an increasing number of H5N1 outbreaks among dairy cows in California. Experts in infectious diseases have cautioned that unprotected contact between dairy workers and infected cows could allow the virus to mutate in a way that poses a hazard to humans since it started infecting the country’s dairy stock in March.
According to Scripps researchers, the time it would take for such a genetic shift to occur would be significantly less than state and federal health officials had predicted.
James Paulson, a molecular biologist and biochemist who coauthored the paper, stated, “This really surprised us.” According to him, this particular mutation meets a criteria for transmission.
The study’s findings, according to Richard Webby, director of the World Health Organization’s Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, challenged conventional wisdom regarding the virus, particularly the idea that it would require several mutations to be dangerous to humans.
Webby, a researcher in the infectious diseases department at St. Jude Children’s Research Hospital in Memphis, Tennessee, who was not involved in the Scripps study, predicted that this would probably create a fuss.
According to Webby, the majority of us believed that multiple changes would likely be required.
According to Yoshihiro Kawaoka, a virologist at the University of Tokyo and the University of Wisconsin-Madison, the Scripps teams’ important discovery was crucial because, considering the rate at which influenza viruses mutate, one out of every 10,000 particles of the bovine H5N1 virus may contain this mutation.
According to him, this suggests that the possibility of an H5N1 virus that can identify human receptors is closer than we may have previously believed.
Paulson and coauthor Ian Wilson, a structural biologist at Scripps, made the decision a few months ago to look at the current strain of H5N1 and determine what it would take for it to spread to humans.
Paulson specializes in studying how and where various influenza viruses attach to cells after infecting a host. Wilson investigates influenza viral protein structure.
In order to find the genetic sequence for the H5N1 avian flu strain A/Texas/37/2024, which was discovered in a dairy worker in Texas, the researchers first accessed a global influenza database.
They then looked at the spikes, or hemagglutinin proteins, on the virus’s outer surface, which allow it to adhere to its host’s cell membrane. Humans and other animals, including birds, contain sialic acid receptors, which are distinct docking stations on their cells. A flu virus requires the perfect spike, or key, to enter a door into a cell and start multiplying.
Despite the fact that H5N1 has infected over 50 people, many of these cases involve dairy workers who were probably exposed to milk from sick cows through their noses and eyes. Scientists believe that this type of repeated exposure enabled the virus to enter cells more forcefully than by picking locks.
According to Paulson, the flu virus typically spreads from person to person through airborne droplets from coughing or sneezing, which contain very little virus. In this case, the virus must be able to identify human-type receptors in order to attach to human airway cells in sufficient quantities to induce infection.
Paulson, Wilson, and their colleagues examined past influenza outbreaks that had crossed the bird-human divide, such as the 1918, 1957, 1968, and 2009 outbreaks, as well as some earlier studies, to determine what it would take for the virus to acquire the proper docking equipment to start a human pandemic.
One by one, they chose amino acids that they knew had been linked to earlier pandemics to alter at various locations on the hemagglutinin protein.
They then tried using human and bird receptor equivalents to bind these modified H proteins.
As it turned out, when they changed a glutamine to a leucine at position 226 it only bound to human receptors and no longer to those of birds.
According to Paulson, it was particularly intriguing because this mutation had previously been found in previous H5N1 strains, including one from approximately 2010, but at that time, a single mutation was insufficient to alter receptor specificity. The surprise aspect is that the virus has evolved, if you will, in subtle ways, so that the receptor specificity is now altered by a single mutation.
Even while the researchers showed that a single genetic alteration may turn the virus into a human threat, that does not imply that nature will choose that particular course. An organism’s evolution can be influenced by a wide range of unpredictable circumstances. Some claim that this is the reason the virus hasn’t been able to infect people on a large scale yet.
We have not observed evidence of this virus adapting to humans on a wider scale, even though bovine H5N1 has infected over 50 humans, Kawaoka stated. This implies that more modifications are probably needed for the virus to become completely human-to-human transmissible.
Paulson agreed that it is crucial to understand the overall biological picture.
He claimed that although the study concentrated on a single characteristic that is critical for the virus to successfully adapt to a new host, other characteristics might also be significant.
For example, H5N1 used to be recognized to induce serious respiratory illnesses. However, in recent years, it has usually been linked to conjunctivitis and infrequently to minor upper respiratory conditions.
Why is that? Paulson remarked, “I don’t think anybody knows.”
We do know that the virus is spreading quickly throughout many species worldwide, giving it plenty of time to change and adapt.
As of Thursday, the Centers for Disease Control and Prevention reported that 58 persons had been verified to have contracted H5N1: 21 from contaminated poultry, 35 from working with sick dairy cows, and two from an unidentified source.
Furthermore, 707 dairy herds in 15 states have contracted the infection. Additionally, 23 commercial poultry farms in California have contracted the virus that affects over 5.6 million birds in the previous 30 days alone.
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Los Angeles Times, 2024. Click here: atlatimes.com. Tribune Content Agency, LLC is the distributor.
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