They are by far the largest herds since outbreaks began last August. They now total more than 100 cases.
There was another outbreak in a herd of 109 pigs in Qingyang city in Gansu province in northwest China, infecting 44 of the animals and killing nine.
The big Siyang county outbreaks infected 2,452 pigs and killed 1,369 of them.
The outbreak in Gansu was the first in that province.
