Mutations discovered in first severe human bird flu case in the US: What we know so far

A new case of severe bird flu in Louisiana has raised concerns about potential mutations in the H5N1 virus. The 65-year-old patient, who is in critical condition after contracting the virus from a backyard flock, has been identified as the first known case of severe bird flu in the United States. According to the Centers for Disease Control and Prevention (CDC), genetic analysis of the patient’s sample revealed mutations in the hemagglutinin (HA) gene, which plays a crucial role in the virus's ability to attach to host cells. These mutations were not present in samples from the infected birds at the patient’s home.

The mutations discovered in the Louisiana patient’s viral sample have raised questions about whether the virus could become more easily transmissible between humans. The HA gene, which facilitates the virus's attachment to cell receptors, underwent changes that may enhance the virus's ability to bind to receptors in the human upper respiratory tract. Normally, H5N1 binds to a receptor that is rare in humans, which limits its ability to infect people. However, these mutations could potentially change that dynamic.

One of the mutations identified in Louisiana was also found in a bird flu virus sample from a teenager in British Columbia, Canada, who was hospitalised in critical condition last month. Although the findings are concerning, scientists emphasise that these mutations are not a sign that the virus has evolved to spread more easily between humans.

Low Risk to the General Public

Despite the concerns, the CDC reassured the public that the risk remains low. There have been no reported cases of the virus spreading from the Louisiana patient to others, and the mutations were not present in the bird samples taken from the backyard flock. This suggests that the mutations developed as the virus adapted to the human host during the course of the infection, rather than originating in the birds.

Dr Scott Hensley, a professor of microbiology at the University of Pennsylvania’s Perelman School of Medicine, explained, "It would have been more concerning if the mutations had been seen in the virus from the birds, because it would have suggested viruses in nature were acquiring these changes." This further suggests that the mutations were not pre-existing in the environment but occurred as part of the virus’s adaptation to the human body.

What Does This Mean for the Future of Bird Flu?

The mutations in question could theoretically make the virus better at binding to human cells, which is an essential step for the virus to infect a person. However, as Dr Michael Osterholm, an infectious disease researcher at the University of Minnesota, noted, “Is this an indication that we may be closer to seeing a readily transmitted virus between people? No. Right now, this is a key that sits in the lock, but it doesn't open the door.” This means that while the mutations may allow the virus to bind more efficiently to human cells, it does not yet suggest the virus can easily spread between people.

Despite the lack of immediate concern, experts warn that every human infection presents an opportunity for the virus to mutate further. As Dr Angela Rasmussen, a virologist at the University of Saskatchewan, cautioned, “More [genetic] sequences from humans is a trend we need to reverse — we need fewer humans infected, period.” She added, "The more humans are infected, the more chances a pandemic virus will emerge."

The bird flu virus, H5N1, has caused sporadic cases of illness in humans, with most infections occurring in people who have had direct contact with infected poultry or wild birds. So far, the virus has not spread easily among humans, which has kept the general risk of a widespread outbreak low. However, the ongoing bird flu outbreaks in poultry and wild birds, particularly in the United States, have led to heightened concerns, especially as the flu season continues.

In recent months, the virus has also been detected in dairy cows, leading to reports of human infections in certain areas. This has contributed to a state of emergency in California and has caused an increase in egg prices nationwide. While these developments are troubling, public health experts continue to stress that the risk of widespread transmission remains low.

In addition to the human cases, there have been reports of pets, including a house cat in Oregon, contracting the virus. The CDC’s ongoing monitoring and research into these cases are crucial for understanding how the virus is spreading and adapting.

The Role of Vaccination

One of the most pressing concerns raised by experts is the availability of vaccines for those at high risk of exposure, such as poultry farm workers. The CDC has stated that the viruses from the Louisiana patient are closely related to candidate strains used in the development of bird flu vaccines. However, Dr Rasmussen has questioned why these vaccines are not being made available to at-risk populations. “What good is that information if we don’t have a plan for how to use it?” she asked.

While the CDC has not indicated an immediate need for widespread vaccination, the increasing number of human infections could make the virus more capable of adapting to human hosts. Therefore, some experts believe that vaccination efforts should be prioritised to help prevent further cases and reduce the risk of a potential pandemic.

Although the discovery of mutations in the H5N1 virus is concerning, experts agree that there is no immediate cause for alarm. The current risk to the general public remains low, and the virus has not yet shown signs of being able to spread easily among people. However, continued monitoring and research are essential to understanding how the virus may evolve. As more cases are reported, particularly in high-risk populations, scientists will continue to track the virus’s genetic changes closely to assess any potential threat.