The world's attention is on a virus right now - the pandemic coronavirus that causes COVID-19. But researchers are still on the lookout for emerging threats, which could still pose a problem.
An influenza virus with 'pandemic potential' has now been identified in a study that assessed nasal swabs from 30,000 pigs in a veterinary hospital and ten slaughterhouses in China between 2011 and 2018. Reporting in the Proceedings of the National Academy of Sciences (PNAS), the researchers isolated 179 viruses from the swine. Some did not show up every year, while others declined over time. But one, called G4 EA H1N1, showed up repeatedly.
The researchers tried to learn more about this virus. Importantly, right now there is no evidence that it can spread from one person to another, so it is nowhere near ready to cause a pandemic. However, they did learn that as many as ten percent of workers on pig farms have been infected with the virus. Though there is zero evidence that it has circulated in people, the scientists found that it can infect human airways. A major question remains: does the virus cause illness?
H1N1 flus are known to be serious - one was responsible for the 1918 pandemic flu. The last swine flu epidemic, in 2009, was not as bad as expected, potentially because older people had immunity that reduced the severity of their infections. Flu vaccines now protect against that virus.
A tweet from Dr. Angela Rasmussen, a virologist at Columbia University's public health school, tweeted that there was no reason to "freak out" about this newly identified flu; there is still a lot of uncertainty about it. She explained that "this virus meets a lot of the basic criteria but it's not for sure going to cause a hypothetical 2020 flu pandemic, or even be a dominant strain in humans." Rasmussen added that we still don't have a complete understanding of what makes a pandemic flu. Importantly, she also noted that even though the authors of the report found antibodies against the virus in people, they did not establish that the virus caused any health problems for those people.
There is no current threat to public health, experts have said. However, some stress that monitoring for the virus should continue. If it does cause illness and eventually begins spreading from one person to another, it could pose a problem.
The study should not be alarming; it is a reminder that we have to stay vigilant. "Pig farming is a massive industry in China and pigs can be important hosts from which novel influenza viruses may emerge," said James Wood, Head of Veterinary Medicine at the University of Cambridge. He also said that this report was a "salutary reminder that we are constantly at risk of new emergence of zoonotic pathogens and that farmed animals, with which humans have greater contact than with wildlife, may act as the source for important pandemic viruses."