Agriculture Secretary Tom Vilsack recently pledged $26.2 million for a variety of efforts to fight the virus, including development of a vaccine. The largest amount, $11.1 million, is to be allocated to helping hog producers with infected herds enhance their biosecurity practices.

The money is badly needed. In an illustration of how indiscriminate the disease is, the virus was found in Vermont in March on a traditional farm with a small drift of pigs raised largely on pasture. “I was not as surprised as one might think,” said Dr. Kristin Haas, the state veterinarian. “Even though in Vermont and most of the Northeast we don’t have the same type of commercial swine operations that you find in Iowa and North Carolina, there is still a tremendous amount of livestock moving in and out of the state.”

Michael Yezzi, proprietor of Flying Pigs Farm just across the border in New York State, said farmers suspected that the virus arrived on a truck from Pennsylvania. “It’s a very big concern because we have young stock on the farm, piglets born on the farm and piglets brought in from regional breeders,” Mr. Yezzi said. “We have to make sure the farms we’re working with don’t have it, because it’s going to kill everything under a certain age.

“Nobody wants to lose 10 to 20 percent of their yearly supply of pigs, whether that would be 150 for someone like me or 15,000 for someone in Iowa.”

Prevention is no mean feat. At the Hord Livestock Company in north-central Ohio, for instance, trucks returning from feed deliveries are cleaned and disinfected and then the trailers are baked to 160 degrees for 10 minutes. Drivers wear disposable bootees, and farm supervisors are not allowed to travel between Hord’s farms.

And yet the company has just finished the four- to five-month process of eliminating the virus from one of its farms and is working to disinfect another and build up its sows’ immunity so they can pass it on to their piglets in their colostrum. The two farms had different strains of the virus, one more deadly than the other.