A new study from Cornell University reveals groundbreaking evidence of mammal-to-mammal transmission of H5N1 avian influenza, highlighting the urgent need for monitoring to prevent future outbreaks.
Researchers at Cornell University have made a significant breakthrough, providing the first evidence of mammal-to-mammal transmission of the highly pathogenic avian influenza H5N1 virus. This discovery could have far-reaching implications for both animal and human health.
The study, set to be published in the journal Nature, documents how the influenza virus spilled over from birds to dairy cattle across various U.S. states. The virus subsequently spread among cows and was transmitted to cats and a raccoon.
“This is one of the first times that we are seeing evidence of efficient and sustained mammalian-to-mammalian transmission of highly pathogenic avian influenza H5N1,” the study’s co-corresponding author Diego Diel, an associate professor of virology and director of the Virology Laboratory at the Animal Health Diagnostic Center in the College of Veterinary Medicine at Cornell, said in a news release.
While whole genome sequencing of the virus revealed no mutations that would enhance H5N1 transmissibility in humans, the observed mammal-to-mammal transmission is concerning.
Diel cautions that the virus might adapt to mammals over time, increasing the risk of a future human adaptation.
“The concern is that potential mutations could arise that could lead adaptation to mammals, spillover into humans and potential efficient transmission in humans in the future,” he added.
To date, 11 human cases with mild symptoms have been reported in the United States. Four cases were linked to cattle farms, while seven were associated with poultry farms, including a recent outbreak in Colorado. The strain in these human cases matches the one circulating in dairy cows, suggesting that dairy farms were likely the origin.
Infections from H5N1 were first detected in January 2022, causing over 100 million domestic bird deaths and affecting thousands of wild birds in the United States. Cornell’s Animal Health Diagnostic Center (AHDC) and the Texas A&M Veterinary Medical Diagnostic Laboratory were among the first to identify the virus in dairy cattle herds. The cows probably contracted the virus from wild birds, leading to symptoms like reduced appetite, changes in fecal matter consistency, respiratory distress and decreased milk production.
Research indicates a high viral tropism for the mammary gland and that infected cows shed significant viral loads through milk. This was further evidenced by the transmission to cats, a raccoon and wild birds, likely through contaminated milk or environmental factors.
The study emphasizes the importance of ongoing monitoring of the virus in both animals and potentially infected humans to prevent further transmission. The U.S. Department of Agriculture (USDA) has funded programs for free H5N1 testing for producers.
According to Diel, early testing, improved biosecurity and quarantines in the event of positive results are critical to containing the virus.
The collaborative study includes contributions from multiple researchers and institutions, including the Texas A&M Veterinary Medical Diagnostic Laboratory and the USDA.
This groundbreaking discovery underscores the necessity for vigilance and proactive measures to mitigate the risks associated with H5N1 transmission and highlights the ever-present potential for zoonotic diseases to adapt and challenge public health on a wider scale.