Rise of dog flu strains could increase risk of next human pandemic, scientists warn

Man’s best friend may be the unwitting delivery system for the next flu pandemic among humans, leading scientists have warned on publication of a new study that found an increase in dog flu strains that could potentially infect people.

Researchers found the virus is now capable of jumping from pigs, one of a handful of species that carries flu, to dogs. They, in turn, can infect humans.

It also found that flu strains were becoming more diverse in canines, in a pattern “very reminiscent” of the events that led to the global swine flu outbreak a decade ago, they said.

The virus has yet to make the jump from dogs to people, but the study’s authors suggested governments should make preparations for controlling the spread of flu in canines, which would increase the risk of a mutant strain crossing the species boundary.

This is particularly important in areas where there are large stray populations and in parts of Asia where they are farmed for meat, they said.

“What we have found is another set of viruses that come from swine that are originally avian in origin, and now they are jumping into dogs and have been reassorted with other viruses in dogs,” said Professor Adolfo Garcia-Sastre, director of the Global Health and Emerging Pathogens Institute.

“The diversity in dogs has increased so much now that the type of combinations of viruses that can be created in dogs represent potential risk for a virus to jump to a dog into a human.”

As new flu strains pass into other species they can swap genes with other infectious diseases native to their host and this increases the virus’s ability to reproduce and cause harm.

In the event that these new strains infect humans they can be very serious as our immune systems haven’t previously encountered them and are slow to fight off the infection.

Advice during bird and swine flu pandemics has been to avoid close contact with the affected animals, although many people are much closer with their dogs than farm animals.

Based at the Icahn School of Medicine in New York, Professor Garcia-Sastre heads up one of five leading centres of excellence in flu research in the US.

He said the “new virus” identified in dogs is H1N1 – the same strain as the 2009 swine flu pandemic.

This strain began in birds, and passed into pigs, but the “antigen” markings on its outer coat – which our immune system uses to spot invaders – are different from the 2009 outbreak.

“We now have H1N1, H3N2 and H3N8 in dogs,” Professor Garcia-Sastre added. “They are starting to interact with each other. This is very reminiscent of what happened in swine 10 years before the H1N1 pandemic.”

For the research, published in the mBio journal of the American Microbiological Society, the researchers analysed the genetics of 16 influenza viruses found in dogs in China’s southern Guangxi region.

Most of these dogs were pets who had been brought to the vet with respiratory conditions, but the large population of street dogs and the dog meat trade makes the spread of infection more likely than in other countries.

They said that governments should begin to consider ways to avert or control any future spread of canine flu. In the UK and US bird flu outbreaks are controlled by culling infected and exposed animals, but doctors are working on a vaccine alternative for swine flu.

“There are attempts to restrict influenza virus in pigs through vaccination and one could consider vaccination for dogs,” Dr Garcia-Sastre said.

A 2015 outbreak of canine flu caused the deaths of at least six dogs in the US and infected thousands.

Jonathan Ball, professor of molecular virology at the University of Nottingham, who was not involved with the research, said it was unlikely we could second guess the next outbreak but a dog source wasn’t impossible.

“Humans have lots of interaction with dogs, and we know that dogs can be infected with influenza,” he added. “What this study provides is evidence that dogs can be naturally infected with multiple strains of viruses, most notably viruses from pigs, which are a known reservoir of influenza viruses that can infect us.

“This increases the potential threat of dogs acting as mixing vessels for the production of new strains of virus that might, just might, in the future spill over into humans.”