The H5N1 bird flu virus, which has infected at least 58 people in the U.S. this year, is raising concerns among scientists. Federal statistics reveal that almost all those infected had close contact with cows or chickens, two species where the bird flu virus mutation is circulating widely. This suggests the virus primarily spreads through close contact with infected animals rather than from person to person.
However, a study published on December 5 in Science warns that the H5N1 strain currently spreading among U.S. cows is only one mutation away from being able to bind more easily to human cells—a critical step toward human-to-human transmission. James Paulson, a professor of molecular medicine at Scripps Research in California and a co-author of the study, emphasized that this mutation is a prerequisite for the virus to spread among humans.
Current Impact of H5N1
H5N1 is currently better at infecting animals than humans. It has caused illness in millions of birds and cows across more than 700 U.S. dairy herds but has infected relatively few humans. Most of the human cases involve farmworkers exposed to high concentrations of the virus through close contact with sick animals.
Troy Sutton, an assistant professor of veterinary and biomedical sciences at Penn State University, explained that while the virus can infect humans in such conditions, it struggles to grow in the human nose and throat. As a result, infected individuals are unlikely to spread the virus to others by coughing or sneezing, which is how seasonal flu typically spreads.
Paulson warned that if the bird flu virus mutates to infect, grow in, and spread between humans effectively, it could trigger a pandemic. His team’s research focused on the first step of this process: how the virus could mutate to bind more easily to human cells.
Bird Flu Virus Mutation Could Change Everything
In their lab study, Paulson’s team analyzed a synthetic version of a gene from the H5N1 strain spreading among cows. They introduced targeted mutations to see how they affected the bird flu virus mutation ability to attach to human cells. Surprisingly, they found that a single mutation could significantly enhance the virus’s ability to bind to human cells.
Previous research had suggested that multiple mutations would be required for such a change. Yoshihiro Kawaoka, a professor at the University of Wisconsin-Madison who studies bird flu, noted that this finding suggests the emergence of an H5N1 strain capable of infecting humans may be closer than previously believed.
Federal health officials are already recommending that high-risk individuals of bird flu virus mutation, such as farmworkers, wear protective equipment when handling potentially infected animals. They are also advising the use of flu antivirals, which appear to work against bird flu, in cases of potential exposure.
Is a Pandemic Imminent?
Despite these findings, Paulson stressed that his study does not indicate an imminent pandemic. The H5N1 virus in its current form does not seem to have evolved to easily target humans. Public health officials also maintain that there is no evidence of person-to-person transmission, and the virus currently poses a low risk to the general public.
Paulson added that more changes would likely be needed for the virus to become highly contagious. While the ability to bind to human cells is an essential first step, additional mutations would be necessary for efficient human-to-human transmission.
Recent cases have, however, raised concerns. A Canadian teenager who contracted bird flu was hospitalized, and scientists analyzing the virus found a mutation similar to the one identified in Paulson’s study. Although the teen did not infect others, this case underscores the potential risk.
Kawaoka’s team also studied a strain of the virus from an infected U.S. farmworker. They found that this strain, which could grow in human lung cells, contained a mutation associated with viral growth in mammals. However, this mutation has not been detected in the strains currently spreading among cows.
Preparing for the Worst
While there is no evidence of person-to-person transmission yet, experts emphasize the need for preparation. Paulson recommends stockpiling bird flu vaccines and developing plans for their distribution if needed. He also stressed the importance of closely monitoring the virus for signs of dangerous mutations.
Sutton highlighted the challenges of identifying a pandemic threat in its early stages. He noted that pandemics are often recognized only after they have already begun, raising concerns about whether health authorities would act quickly enough if they detected the key mutation identified in the study.
The findings serve as a reminder of the constant need for vigilance and proactive measures to prevent potential public health crises.
