A dangerous virus is just one mutation away from becoming a threat to humans
A dangerous virus is just one mutation away from becoming a threat to humans
6.12.2024., 9:01
At least 58 people in?the U.S.?have been infected with the?H5N1 bird flu?virus this year , and all but two of them were near cows or chickens - two types of animals in which H5N1 circulates widely,?Time?reports .
While this is reassuring to scientists because it suggests that the virus primarily spreads through close contact with infected animals rather than person-to-person, the results of a study published Dec. 5 in the journal Science are less comforting. Namely, the H5N1 strain, which is spreading among cows in the USA, is only one specific mutation away from easily binding to human cells, which is a prerequisite for transmission between humans. This is claimed by a scientist who collaborated in the research - author?James Paulson?, a professor in the department of molecular medicine at Scripps Research in California.
In its current form, the H5N1 virus infects certain animal species more easily than humans. It has sickened millions of birds and cows from more than 700 dairy herds in the US, but relatively few people.
Most of these cases of infected people were among farmers. This, Time writes, suggests that although the bird flu virus is not very contagious to humans, it sometimes finds a way when humans are exposed to high enough concentrations of the virus, as in the case of close contact with sick animals, explained?Troy Sutton?, associate professor of veterinary and biomedical sciences. at Penn State University, who was not involved in the new study.
However, because the virus doesn't have a good chance of growing in the human nose and throat, people who get sick don't seem to be able to easily infect other people by coughing or sneezing, as happens with the common seasonal flu, Sutton says. Paulson argues that "a pandemic could begin" if bird flu changed enough to effectively infect, grow and "jump" between humans.
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A dangerous virus is just one mutation away from becoming a threat to humans
A surprising discovery
His team focused on the first step in that process: how the virus would need to change to bind more easily to human cells. In the laboratory, they studied the synthetic form of the gene from the strain of the virus that is currently circulating among cows. They made targeted mutations to see how the shifts changed its ability to bind to human cells. Paulson said the "surprising finding" is that one specific mutation appears to be sufficient. Previous research into the H5N1 virus, including Paulson's, suggested more changes would be needed.
"The emergence of a bovine H5N1 virus capable of recognizing human receptors may be closer than previously thought,"?Yoshihiro Kawaoka?, a professor at the University of Wisconsin-Madison who studies bird flu but was not involved in the new study, told Time.
It's a "surprising" finding, Sutton agrees, and a good motivator to prevent further human cases as much as possible. Federal health officials already recommend that high-risk people, such as farmers, wear personal protective equipment around animals that might be sick and take antiviral flu medications in case of exposure, which also appear to work against bird flu.
Paulson, however, stresses that his study does not mean a pandemic is inevitable. Despite what his team discovered in the lab, the virus circulating in the real world does not appear to have evolved enough to easily infect humans. Public health officials say the virus is not spreading from person to person and currently poses a low risk to the general public.
And while health officials are closely monitoring the situation, some troubling observations have already been made. A Canadian teenager was recently hospitalized after contracting bird flu. After scientists analyzed the genetic sequence of the virus taken from the teenager, they reportedly found that it had mutated in a way that could make it more transmissible between people, similar to the mutation that Paulson's team identified in their study. Fortunately, the teenager does not appear to have infected anyone else.
Kawaoka also studied a strain of the virus taken from an infected American farm worker. That strain, which was able to grow in human lung cell samples, contained a mutation known to promote virus growth in mammals. But that mutation is not seen in strains of the virus that spread among cows, his team noted when the study was published in October.