In a startling development, researchers have identified a genetic mutation of the H5N1 bird flu virus in two domestic cats, indicating a significant rise in both infectiousness and severity of disease. This finding serves as a warning about the evolving nature of the virus and its potential risks to animals and possibly humans.

Seema Lakdawala, a microbiologist at Emory University in Atlanta, expressed her concerns, stating, “The detection of this mutation in cats is a clear example of the virus's evolution and should alarm everyone.” This underscores the importance of ongoing surveillance and understanding of how bird flu variants might impact various species, including pets.

The mutation, known as PB2 E627K, has been linked to increased transmissibility among mammals and heightened disease severity as observed in laboratory studies. This particular mutation shares similarities with a mutated strain found in dairy cows in San Bernardino earlier this week but arises from a different virus lineage. The infected cows, detected with the B3.13 strain of H5N1, have been spreading the virus since last March. Meanwhile, the cats were found to carry the more recent D1.1 strain, which has primarily circulated among wild birds, and has also recently affected cattle herds in Nevada and Arizona.

Reports indicate that these infected cats are likely from New Jersey, having contracted the virus last month. The New Jersey Department of Public Health recently announced a cluster of infected felines in Hunterdon County, where both cats resided. While one was a feral cat, the status of the other cats involved remains uncertain.

The United States Department of Agriculture has reported a troubling uptick in H5N1 infections among felines, with 51 cases recorded since the start of 2025 alone, affecting pets and wild cats across 13 states. This includes notable states such as California, Montana, and New Jersey. The total number of reported cases since the outbreak began in dairy cows exceeds 100, highlighting an increasing trend that cannot be overlooked.

On February 28, a press release disclosed that all infected cats shared the same property and noted that it remains unclear if any of the additional four cats were also infected. Furthermore, the New Jersey health department confirmed that there have been no human infections recorded in connection with these cases, with individuals who had contact with the cats remaining asymptomatic.

The genetic sequences from the two cats were recently uploaded to GISAID, a global repository for influenza data, allowing scientists worldwide to monitor and study these viral changes closely.

Richard Webby, an infectious disease specialist at St. Jude’s Hospital in Memphis, commented on the findings, noting that while the emergence of this mutation isn't unexpected, it does warrant vigilance. He stated, “This mutation has appeared sporadically in other mammals over the last few years. We must remain cautious, especially if its prevalence escalates.”

As the situation develops, it is critical for pet owners to remain informed and take precautions. The question remains: what implications might this have for animal and human health moving forward? Stay tuned as we uncover more about this evolving health story!