As global health experts closely monitor the evolving landscape of infectious diseases, new research from the University of Maryland raises alarms over a surge in avian influenza (bird flu) infections in cats and the potential implications for human health.
A comprehensive global review, spanning 20 years of published data (2004–2024), has revealed a dramatic rise in bird flu infections among cats, particularly since the emergence of H5N1 clade 2.3.4.4b, a highly pathogenic strain previously linked to outbreaks in wild birds and mammals.
Alarming Statistics
The study, published in Open Forum Infectious Diseases, analyzed 48 scientific articles and identified 607 cases of avian influenza in 12 feline species, including pet cats, bobcats, caracals, lions, and tigers, across 18 countries. Notably, more than 70% of the PCR-confirmed infections were fatal, with 62.6% of all cases occurring in domestic cats.
The highest concentration of cases was reported in Asia (50%), followed by Europe (25%) and North America (16.7%).
What’s particularly concerning is the rapid increase in feline infections in 2023 and 2024, which researchers say mirrors the wider spread of the H5N1 clade 2.3.4.4b in birds and mammals.
New Transmission Routes Emerging
While bird-to-cat transmission through ingestion of infected birds has been the most common route, researchers are now observing new and poorly understood transmission pathways. For instance, two recent cases in Colorado involved indoor-only cats with no known exposure to infected animals. Additionally, infections have been traced to cats drinking raw milk or colostrum from cows infected with H5N1, suggesting that contaminated food sources may be playing a growing role.
“These cases raise concerns about silent transmission routes,” the authors wrote, emphasizing the need for heightened surveillance.
High Fatality, Neurological Impact
The virus has proven especially lethal in cats. Among HPAI H5N1 infections, the case fatality rate was over 52%, and for the newer clade 2.3.4.4b, it spiked to nearly 90%. Symptoms often include respiratory distress, blindness, and encephalitis, and in many cases, these signs are misdiagnosed as rabies due to overlapping neurological symptoms.
This diagnostic confusion adds to the concern that feline cases are widely underreported, particularly in shelters, farms, and rural areas.
Spillover Risk to Humans
Though there has been no confirmed human-to-human transmission of avian flu to date, the virus has infected at least 950 people globally, half of whom have died. In the United States, 66 cases have been reported between April 2022 and January 2025, with one fatality.
Lead author Dr. Kristen Coleman of the University of Maryland warns that the virus is mutating in troubling ways:
“The way it jumps between species—from birds to cats, now cows to cats, and potentially cats to humans—is very concerning. As summer approaches, we are anticipating cases on farms and in the wild to rise again.”
Shelters and farms may be particularly vulnerable, and cat-to-human transmission, though rare, has been documented.
Urgent Call for Monitoring
Cats are not routinely tested for avian flu, and testing usually occurs postmortem. This lack of surveillance, combined with growing evidence of subclinical or atypical infections, presents a significant blind spot in our pandemic preparedness efforts.
The study authors call for urgent monitoring of domestic and shelter cats, particularly in high-risk environments like farms, zoos, and rural areas. They also advocate for testing of raw animal products, such as milk and poultry feed, which may harbor high viral loads.
Conclusion
The findings serve as a stark reminder that in an interconnected ecosystem, veterinary, agricultural, and human health are deeply entwined. Monitoring animals, especially those in close contact with people, is not just a veterinary issue but a public health imperative.
As Dr. Coleman puts it, “We want to help protect both people and pets.”
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