A nasty virus called African swine fever has spread from pig farms in Africa to China.

The number of pigs China will fatten this year is predicted to fall by 134 million, or 20%, from 2018—the worst annual slump since the U.S. Department of Agriculture began counting China’s pigs in the mid-1970s. While the pig virus doesn’t harm humans even if they eat tainted pork, the fatality rate in pigs means it could destroy the region’s pork industry.