Some researchers say that although the chances of that happening appear minimal, the implications are too grave to dismiss. In a commentary published Thursday in the Lancet Microbe, researchers at University College London called for widespread surveillance of pets, livestock and wildlife. Studies on animal susceptibility have been small, limited and, in the case of pigs, conflicting, they wrote.

“We need to develop surveillance strategies to ensure we don’t get taken by surprise by a large outbreak in animals, which could pose a threat not just to animal health but to human health as well,” co-author Joanne Santini, a professor of structural and molecular biology, said in a statement.

The steps being taken in the Netherlands, which also include surveillance of cats at the farms and wild mink relatives called martens, are among the broadest efforts to understand how a zoonotic virus that originated in animals before hopping to humans may now be spreading back to animals. In the six months since the outbreak began, cases have been reported of human transmission to dogs, cats, tigers and lions in addition to minks. Laboratory experiments have found that ferrets, hamsters, monkeys and other mammals are also susceptible to the virus.