When birds infect mammals: The looming threat of avian flu Experts warn of potential pandemic as avian influenza strains evolve to jump species barriers


Health officials and scientists around the world are sounding the alarm over rising cases of avian flu spillovers to humans. Spillovers occur when a virus jumps from one species to another — in this case, from birds to mammals. As avian influenza (influenza A) strains evolve and break species barriers, experts warn of the potential for a devastating pandemic that could rival or surpass the current COVID-19 crisis.

According to the World Health Organization (WHO), there are four predominant types of influenza viruses: A, B, C, and D. Influenza A viruses infect humans and food-producing birds such as chickens, turkeys, and quails. Influenza B circulates most commonly among adults and can cause seasonal epidemics. Influenza A has been known to show more severity in its symptoms as compared to B. Influenza C has the potential to infect humans and pigs; however, infections are generally mild as compared to influenza D, which affects cattle and is not known to infect people. 

The “avian flu” or “H5N1” has potential for human to human transmission, resulting in an influenza pandemic. This strain has two types: low pathogenic and high pathogenic. 

The Government of Canada noted that avian influenza is divided by subtypes based on two proteins found in the virus: hemagglutinin, or the “H” protein, and neuraminidase, or the “N” protein. In general, there are 16 “H” types and nine “N” types which create a total of 144 possible combinations. 

The concerning subtypes are H5 and H7 as they have the ability to mutate from low pathogenic to highly pathogenic after they infect domestic birds. They have been known to cause serious disease or mortality in domestic poultry. These strains are a cause for concern because they must be reported to chief veterinary personnel and health agencies under the public health guidelines.   

The WHO recently issued a warning about bird flu spillover to mammals. It mentioned that it needs to be monitored closely and that countries need to be prepared for a potential human outbreak. 

Even though the H5N1 has existed for 25 years, it has recently crossed into small mammals like minks, foxes, otters, and sea lions.  

Christine Dupont, a biologist at the University of Waterloo and an expert in pathobiology, shared her concern over the fact that the strain doesn’t seem like regular bird influenza. 

“It’s a highly pathogenic avian influenza. Bird influenza is common, and these viruses evolve quickly. It’s monitored intensely because there is potential for bird flu to become a human pandemic,” Dupont said. 

When asked about the concerns over the spillover factor of the virus, she shared her thoughts. 

“Spillover events are a worry, especially when you’ve got a virus like this that’s highly contagious among birds and causing infection in a lot of different organ tissues. And if it has been moving into other animal species, that means it could also not just jump the tissue barrier, but the species barrier. We know in the past that every pandemic we’ve had with influenza, like the swine flu and the Spanish flu, had their origins from spillover events that can all trace back to aquatic birds,” Dupont said. 

As the situation continues to develop there are more instances coming forward revolving around new cases of bird flu. From dead birds being found in parts of the province now to chicken farms being put on red alert, the cause for suspicion rings up to the avian flu.