The U.S. government has begun scattering millions of packets of oral rabies vaccine from helicopters and planes in 13 states from Maine to Alabama.
The major aim is to help keep raccoons from spreading their variant of the deadly virus to states where it's less prevalent.
The government is also continuing tests of a vaccine that Canada has approved to immunize skunks as well as raccoons.
Rabies is generally spread through an infected animal's saliva. In the U.S., pet vaccination laws mean it's mostly spread by wildlife.
Federal experts say 60,000 Americans a year get rabies shots after being bitten or scratched by an animal that's infected or might be.
The national rabies control program started in 1997 in Texas, where coyotes were spreading the canine variant of the virus.
A three-year program in Arizona and New Mexico eliminated a bat rabies strain in foxes, according to wildlife officials. The USDA dropped 1.1 million baits along the Mexican border in January to keep coyotes from bringing the canine variant back.
Raccoons are the main rabies reservoir in 18 states along and near the East Coast and skunks in 21 others, according to data from 2020, the latest year available.