Last year's H1N1 pandemic may have been milder than global health experts had feared, but this is no cause for complacency. Researchers in Hong Kong reported today in the online journal Science that the virus is rampant in pigs throughout China. In fact, HIN1 has already mixed with other flus there and emerged in pigs as a new strain. The danger, of course, is that this strain—or a future one—could infect people.

“Just because we’ve just had a pandemic does not mean we’ve decreased our chances of having another,” Carolyn B. Bridges, an epidemiologist at the Centers for Disease Control and Prevention, told the New York Times. “We have to stay vigilant.”

The health experts in Hong Kong called for more careful monitoring of flus in hogs, so that they can better assess their possible transmission to people.  Michael Worobey, an evolutionary biologist at the University of Arizona, called for more extensive testing of pigs when he participated last summer in Big Think's panel discussion on pandemics.  Worobey was part of a team of researchers who discovered that H1N1 itself had been circulating undetected in pigs for at least a decade.