Dogs May Be ‘Patient Zero’ for Future Canine Influenza Outbreaks With Human Spillover: Study 2023

China’s scientists have identified strains of the influenza A-H3N2 virus circulating in canines that may soon be able to infect humans.

Animal reservoirs of influenza A viruses have repeatedly crossed species barriers to infect humans. Viruses that cause H3N2 avian influenza or bird flu were transmitted to dogs for the first time around 2006 and have since formed stable canine lineages.

More than 4,000 dog samples were analyzed by a team from the China Agricultural University.

The findings, which were published in the journal eLife, demonstrated that the H3N2 canine influenza viruses (CIVs) can recognize human-cell receptors and have the ability to replicate in humans.

“We found that, during adaptation in dogs, H3N2 CIVs gained the ability to recognize the human-like receptor and gradually increased their hemagglutination (HA) acid stability and replication ability in human airway epithelial cells,” they wrote.

In addition, they discovered that “human populations lack immunity to H3N2 CIVs, and even immunity derived from current human seasonal influenza viruses cannot provide protection against H3N2 CIVs.”

“Our findings indicate that canines may play a role in the adaptation of avian influenza viruses to humans. Continuous surveillance coordinated with risk assessment is required for CIVs, according to researchers.

To evaluate the infectiousness and transmissibility of H3N2 CIVs in dogs, the team purposefully inoculated six dogs with known strains of canine influenza.

The dogs became mildly unwell, with fever, sneezing, wheezing, and coughing being the most severe symptoms.

While no human infections have been reported with H3N2 CIVs to date, the team warns that “dogs may increase the likelihood of viral cross-species transmission to humans.”

According to experts, the research emphasizes the role of pet dogs as a potential “patient zero” for a future outbreak of dog flu, as reported by The Telegraph.

Prof. James Wood, head of the University of Cambridge’s department of veterinary medicine, was quoted as saying that it is “pretty clear” that the bird flu H3 strain has mutated into a canine-specific virus.

“The changes in the canine virus are apparently making it better adapted to transmit within mammals, as you might expect after such a long period in dogs,” he noted.