There's no real correlation between size and disease. It can hit any pig. It could be two pigs in a facility or 10,000 pigs in a facility. But the amount of shedding of the virus once that facility gets sick is obviously a lot more when there are a lot more animals. The virus becomes airborne and there's lots of virus to infect surrounding sites.
On June 15th, 2017. See this statement in context.