HARRISBURG, Pa. (WHTM) — The U.S. Department of Agriculture says the avian flu situation in the Midstate is improving.

4,194,600 birds have been killed to stop the spread in Pennsylvania.

Pennsylvania has been the third hardest hit state in the U.S. Because avian flu is highly contagious, control zones were setup to contain the spread.

The avian flu outbreak has affected 16 commercial flocks in Pennsylvania.

Right now, five control zones are in Lancaster County and six in Berks County.

“Making sure that they keep their premises free of movement from other people, using bio-security and movement and sharing that information because we all to work together to get this done,” said Dr. Fred Soltero, USDA incident commander.

Soltero says the heat is helping.

“We are having a very good weather bout. The virus doesn’t like the hot weather.”

He says they’re working closely to see if they can release some zones this week but it takes a lot of data and bio-security assurance to do so.

“Usually it takes about a month or month and a half of testing, cleaning the area, making sure we did all the environmental swabs so we can assure that control area has been tested enough, that we have not found a case and we can declare it free,” Soltero said.

But that doesn’t mean the virus won’t return to that area.

“We need to make sure that owners then follow a process of permitting which is to request the legal or controlled movement of animals,” Soltero said.

Soltero still wants people to be vigilant and call the USDA if there are any issues.

“If you know of people that have mortality in their flock or have any kind of information that we should know, please contact us as fast as possible,” Soltero said.

Soltero says the improvements are happening everywhere in the U.S. Some states are now in the clear.