New flu variant emerging out of China
In this DML Report…
A new variant of the Influenza D virus, known as D/HY11, emerged in cattle in northeast China in 2023, with retrospective serum analyses revealing circulation in the region since at least 2020. This virus primarily infects livestock including cattle, pigs, and swine, but laboratory tests show it replicates efficiently in human airway cells, as well as in cells mimicking the nasal passages, trachea, and lungs of humans, cows, pigs, and dogs, reaching high concentrations across these regions over 96 hours. It transmits efficiently through the air between cows and ferrets—a model for human transmission—without direct contact, a trait linked to potential easy spread among mammals. No routine testing for IDV occurs anywhere in the world, allowing for possible undetected circulation.
Animal studies demonstrate further risks: infected mice showed virus spread to organs including the brain, dogs shed the virus indicating transmission potential, and ferrets exhibited airborne spread from infected to healthy individuals. Blood tests from archived samples in Northeast China found 74 percent of people—both urban and rural—had antibodies to the virus, suggesting animal-to-human jumps, with the rate rising to 97 percent among those with recent respiratory symptoms. Researchers note accumulating mutations in D/HY11, including heightened activity in its polymerase replication machinery, that could adapt it for sustained human circulation, though it remains unknown whether it spreads between people or if exposures represent isolated infections. The team concludes: "This raises the possibility of cryptic transmission in humans with mild or asymptomatic infections via the emerging D/HY11-like viruses," and states, "In summary, it is likely that IDV outbreak has metastasized into an ongoing problem for cattle and humans."
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The virus proves susceptible to newer antiviral drugs like baloxavir that target RNA polymerase but resistant to common flu medications such as Tamiflu. Led by researchers at China's Changchun Veterinary Research Institute, the study was published in Emerging Microbes & Infections. Post-Covid, a global network of researchers and public health officials monitors animal viruses with pandemic potential through genetic sequencing in wildlife and serum testing in humans to develop treatments and vaccines. Concerns persist over silent spread of this panzootic virus and the emergence of new varieties due to inadequate surveillance, with widespread exposure in Northeast China underscoring an ongoing threat to both livestock and human health if adaptations continue.