An evolved swine flu virus might attack us again, new study reveals

There is a chance swine flu might evolve and hit back at humans, but if we could limit the spread of the virus in people who work closely with swine, we can prevent any such event.
Rupendra Brahambhatt
A researcher testing a pig for swine flu virus.
A researcher testing a pig for swine flu virus.

M.Marti and A.Grimes, USDA

The first case of swine flu (H1N1pdm09) in humans was reported 14 years ago in 2009. According to CDC, the virus killed somewhere between 151,700 to 575,400 people across the globe, and even at present, it continues to spread seasonally as a regular flu virus in humans.

A new study suggests that pdm09 has passed from humans to pigs 370 times since its emergence. The repeated circulation of the virus in pigs from humans may have allowed it to evolve further. Therefore there is a risk that an evolved pdm09 might infect humans and cause another outbreak.

“Our analysis confirmed that pdm09 frequently causes the interspecies barrier between humans and swine,” the researchers note. 

Is there a risk of a new swine flu pandemic?

Swine flu (H1N1pdm09) is a type A virus (influenza A virus or IAV) that can spread to pigs, humans, birds, dogs, cats, and other mammals, including whales. The researchers suggest that the transmission of the virus in different animals can lead to changes in its genetic composition. 

Their study analyzed the risk of an evolved pdm09 infection in humans from pigs. They studied the data related to the transmission of the swine flu virus from 2009 to 2021 and noticed that during this time, about 370 times pdm09 made its way to pigs via humans.

Even during COVID-19, when the circulation of the pdm09 virus among humans was low, it was stable in swine. However, about 40 percent (150) of human-to-pig transmission events took place in the years before the COVID-19 pandemic, i.e., between 2018 and 2020.

Although most of these events didn’t seem to trigger any evolutionary changes in the virus, a few of them caught the attention of the researchers. These few transmission events caused the persistent circulation of genetically advanced pdm09 variants in the pigs

The researchers confirmed at least five instances when they reported such variants. Surprisingly, the new variants could evade the protection the seasonal swine flu vaccine offers.      

“Our data demonstrate that pdm09 viruses established in US swine have drifted away from human seasonal vaccine strains, potentially reducing human population immunity to them,” they added.

We need not fear but manage the risk 

The study highlights the risk of an evolved swine flu virus, but at the same time, these findings also reveal a promising strategy to prevent the spread of a powerful pdm09 in humans from pigs. 

The data from the study hints that if we manage to control the transmission of the virus in people who regularly interact with swine (like farmers), we can minimize the circulation of pdm09 in pigs and thus prevent it from evolving further.   

“Controlling influenza A virus infection in humans can minimize the spillover of viruses into pigs and reduce the diversity of viruses circulating in swine populations. Limiting virus diversity in pigs can minimize the emergence of novel viruses and the potential for swine-to-human transmission of influenza A virus,” said the study authors.

Hopefully, the findings from this research work will help us avoid any possible swine flu outbreaks in the future.