A nearly decade-long study of Chinese pigs has found a potentially dangerous new type of influenza virus.

The research, published today in the journal Proceedings of the National Academy of Sciences , describes a flu strain that shares genes with the one that caused the 2009 swine flu pandemic.

The virus is a combination of three flu strains, the scientists found: one from European and Asian birds, the flu strain that caused the 2009 swine flu outbreak, and a North American flu that has genes from bird, human, and pig flu viruses.

The new strain could pose a major threat if it jumps to humans, the researchers warned, though it hasn't yet. Plus, because it contains parts of the 2009 swine flu , it "may promote the virus adaptation" that leads to human-to-human transmission, the researchers wrote.

Given the devastation that the coronavirus pandemic has caused, the researchers said, it's critical to take proactive measures now to protect people against this swine flu, they added.

A medical staff member is seen next to a patient suffering from the coronavirus disease (COVID-19) in the intensive care unit at the Circolo hospital in Varese, Italy April 9, 2020.
A medical staff member is seen next to a patient suffering from the coronavirus disease (COVID-19) in the intensive care unit at the Circolo hospital in Varese, Italy April 9, 2020.
REUTERS/Flavio Lo Scalzo

An emerging new type of swine flu

Identifying new virus strains in pigs is crucial for preventing another pandemic.

The 2009 H1N1 pandemic was caused by an Influenza A virus that emerged from pigs. The animals can serve as a reservoir for infectious diseases, since they can be infected with bird, pig, and human influenza strains. When multiple strains of influenza infect the same pig, the viruses can swap and replace genes, a process known as "reassortment," leading to the creation of a new disease.

The team of Chinese researchers that conducted this study aimed to identify those types of potentially dangerous, never-before-seen viruses in pigs. The work that led them to find this new strain began in 2011 and continued through 2018. They took nearly 30,000 swabs from pigs in slaughterhouses in 10 Chinese provinces, and another 1,000 swabs from pigs with respiratory symptoms at a local veterinary teaching hospital.

The researchers found 179 virus strains in Chinese pig populations, but this one stood out.

Pig on farm in China
Pig on farm in China
Thomas Suen/Reuters

They named the worrisome new flu strain G4 EA H1N1. That virus has emerged on a larger scale in swine populations since 2016, according to the study it's "the predominant genotype in circulation in pigs detected across at least 10 provinces," the researchers wrote.

They added that the virus is "distinct from current human influenza vaccine strains, indicating that preexisting immunity derived from the present human seasonal influenza vaccines cannot provide protection."

In testing the virus in a lab, they found that it reproduces in the respiratory system. It can spread among animals through small airborne particles. It also transmits easily among ferrets, a species scientists frequently use as an indicator of how bad viruses may be in humans. (Ferrets display human-like flu symptoms when infected.)

"Controlling the prevailing G4 EA H1N1 viruses in pigs and close monitoring in human populations, especially the workers in the swine industry, should be urgently implemented," the researchers wrote.

coronavirus vaccine
coronavirus vaccine

The threat of another swine flu pandemic

H1N1 emerged at the end of 2008 and infected approximately 60.8 million people in the US through 2010. It was referred to as "swine flu" because it originally jumped from pigs to humans .

Estimates of total global H1N1 deaths range from 151,700 to 575,400. But H1N1 differed from other influenza outbreaks in that 80% of the virus-related deaths occurred in people younger than 65. (Between 70% and 90% of deaths from influenza outbreaks typically occur in those older than 65.)

In total, scientists think mammals and birds around the globe host about 1.7 million undiscovered types of viruses . Viruses in birds, bats, and pigs are especially risky for people.

China has the world's largest pig population about 310 million, according to Statista . So Chinese scientists monitor them in an attempt to find emerging diseases before they spread.

"Systematic surveillance of influenza viruses in pigs is essential for early warning and preparedness for the next potential pandemic," the researchers behind the new study wrote.

pig farm
pig farm

Their surveillance has uncovered other concerning trends, too: They found that the portion of pigs studied that had diseases increased over time. The number rose from 1.4% in 2011 to 8.2% in 2018, with a sharp increase after 2014.

A similar surveillance system also exists for coronaviruses. Scientists believe that the new coronavirus, known SARS-CoV-2 jumped to people from bats, likely via an intermediary animal species.

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