Reston ebolavirus, or REBOV, was originally identified in 1989 in the United States from a shipment of cynomolgus monkeys from the Philippines, but unlike other types of Ebola, it is not yet known to cause illness in humans.

Currently, it isn't clear whether REBOV could become as virulent in humans as other types of Ebola, but the researchers said it is hypothetically possible that the virus could mutate in pigs and threaten humans.

"REBOV infection in domestic swine raises concern about the potential for emerging disease in humans and a wider range of livestock," the researchers wrote in Friday's edition of the Journal Science.

"There is concern that its passage through swine may allow REBOV to diverge and shift its potential for pathogenicity," they said.

Some pig farm workers in the Philippines have also become infected, though they show no obvious symptoms of human disease, the researchers noted.