aAt least 58 people have been infected with the H5N1 avian influenza virus in the United States this year. According to federal statistics. All but two of the animals had been around cattle or chickens where H5N1 is widely prevalent. it is Peace of mind for scientists That's because it suggests the virus is primarily spreading through close contact with infected animals, rather than from person to person.
The less pleasant result is the study Published in a magazine on December 5th science: The H5N1 strain spreading among cattle in the U.S. has just one specific mutation that allows it to easily bind to human cells, a “prerequisite for human-to-human transmission,” says study. said co-author James Paulson, a professor in the Department of Molecular Medicine at Scripps Research in California.
In its current form, the H5N1 virus is better at infecting certain animal species than humans. Millions of birds and cows are sick on more than 700 U.S. dairy farms, but the number of people affected is relatively small.
Most of those human cases are farm worker. This means that although the avian influenza virus is not very contagious to humans, it is possible for humans to become infected if they are exposed to a sufficiently high concentration of the virus, such as through close contact with sick animals. Troy Sutton, an assistant, explains that this suggests that there is a gender. He is a professor of veterinary medicine and biomedical science at Penn State University and was not involved in the new study. However, this virus does not grow well in the human nose and throat, so person who gets sick Sutton said it doesn't appear to be easily spread to others through coughing or sneezing, like the regular seasonal flu.
If avian influenza becomes effective, multiplies in the body, and changes enough to jump from person to person, “that's the start of a pandemic,” Paulson said.
His team focused on the first step in the process: how the virus needs to change to easily bind to human cells. In the laboratory, they studied a synthetic version of the gene of a virus strain currently circulating among cattle. They created targeted mutations to see how the changes altered its ability to attach to human cells. “The surprising discovery was that one specific mutation seemed to be sufficient,” Paulson said. Previous research on H5N1, Including Paulson.suggested that further changes would be necessary.
“The emergence of a bovine H5N1 virus that can recognize human receptors may be closer than we previously thought,” says the University of Wisconsin-Madison professor who studies avian influenza and is involved in the new study. Yoshihiro Kawaoka, who was not involved, wrote in an email. Until the hour.
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Sutton agrees that this is an “astonishing” finding and a good incentive to prevent further human infections as much as possible. Federal health officials have already advised high-risk populations, such as farm workers, to wear personal protective equipment around potentially sick animals and to administer anti-influenza medications ( It seems to be effective against bird flu).
Still, Paulson emphasizes that his study does not mean a pandemic is imminent. Despite what his team has discovered in the lab, viruses circulating in the real world don't seem to have evolved to easily target humans. Public health officials maintain that the virus is not spreading from person to person and the risk to the general public is low at this time.
Further changes may be needed for the virus to pose a true pandemic threat. Paulson's team's ability to easily bind to human cells is just the first step toward widespread human-to-human transmission, he says. Further changes may be needed for the virus to become highly contagious in the real world.
Mr. Kawaoka agrees. Although more than 50 people have become ill in the United States, the fact that health officials have not seen evidence of human-to-human transmission means that “further mutations are necessary for the virus to effectively spread from person to person.” This suggests that it is likely necessary. ” he wrote.
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Health authorities are closely monitoring the situation and several worrying observations have already been documented. A Canadian teenager was recently hospitalized with bird flu. Scientists analyzed the genetic sequence of a virus taken from a teenage boy. I found out that it has changed This is similar to the mutation that Paulson's team identified in their study, which could make it more transmissible between humans. (But fortunately, this boy does not seem to have infected anyone else.)
Professor Kawaoka also studied virus strains taken from infected US farm workers. Kawaoka and his team found that the strain was able to grow in samples of human lung cells and contained mutations known to promote virus replication in mammals. . However, this mutation has not been observed in the virus strain spreading among cattle. his team emphasized when research has been published In October.
Although there is no evidence yet of human-to-human transmission, health officials need to prepare for a wider spread of bird flu as a precaution, Paulson said. It's worth stocking up avian influenza vaccine And he says he has plans for how to deploy them if the need arises.
It's also important to continue to monitor the virus closely for signs of change, Sutton said. But “what's alarming to me is that we often find ourselves in a pandemic only after it starts,” he says. “Once we start seeing this mutation, is it already too late? We don't know the answer to that.”
