Earlier this year, scientists identified a new strain of swine flu that they said had "all the essential hallmarks of a candidate pandemic virus."
As well as finding that the virus — termed G4 — was highly infectious, they also discovered that 10.4 percent of workers who dealt with the pigs had antibodies for the disease, showing that transmission to humans was possible. However, there is no evidence yet that the virus can pass from person to person.
In the paper, published in PNAS, they wrote that pigs are important "mixing vessels" for influenza viruses with the potential to infect humans, and so monitoring emerging viruses in pigs provides an essential early warning for strains that could go on to become a pandemic.
Enter another potential zoonotic pathogen with an alarming sounding name. In a new study from the University of North Carolina at Chapel Hill, researchers have taken a closer look at yet another virus in pigs with the potential to spread to humans. The highly pathogenic virus, called swine acute diarrhea syndrome coronavirus (SADS-CoV), first emerged in bats before infecting herds of swine throughout China in 2016.
The team, publishing their findings in PNAS, injected a synthetic version of SADS-CoV into different cell types in the lab in order to determine if it could replicate in human cells, including human liver, lung, and intestinal cells.
"Of concern, rSADS-CoV also replicated efficiently in several different primary human lung cell types, as well as primary human intestinal cells," the team wrote in the paper. "Efficient growth in primary human lung and intestinal cells implicate SADS-CoV as a potential higher-risk emerging coronavirus pathogen that could negatively impact the global economy and human health."
The virus replicated at a higher growth rate within intestinal cells; this is unlike SARS-CoV-2, the virus that causes Covid-19, which mainly infects lung cells. However, though it needs monitoring, the virus has not yet been found to infect humans outside of a lab setting. The team also tested broad-spectrum antiviral remdesivir — which has also shown promise for treating Covid-19 — and in preliminary results found that it "efficiently blocked rSADS-CoV replication in vitro."
"Promising data with remdesivir provides a potential treatment option in the case of a human spillover event," Caitlin Edwards, a research specialist and master of public health student at UNC-Chapel Hill, said in a statement. "We recommend that both swine workers and the swine population be continually monitored for indications of SADS-CoV infections to prevent outbreaks and massive economic losses."
The team are now looking into potential vaccines for the virus to protect swine herds.
"While surveillance and early separation of infected piglets from sows provide an opportunity to mitigate larger outbreaks and the potential for spillover into humans," Edwards said, "vaccines may be key for limiting global spread and human emergence events in the future."