Dozens of cats were euthanized to prevent the spread of a highly contagious and fatal virus carried by cats rescued from a woman police are calling a hoarder, Fairfax County authorities said Thursday.

Around 75 cats were rescued from a Springfield home in mid-June, said Fairfax County police spokesperson Mary Ann Jennings. They were found to carry a virulent strain of the respiratory ailment calicivirus, and all 80 cats in the Fairfax County Animal Shelter were euthanized Wednesday to prevent further infection.

Other animal rescue groups that helped take in some of the cats from the hoarding incident also had to euthanize cats in their facilities, said Jennings, who did not know the total number of infected cats.

The virus, which Jennings said has been spotted in other regional shelters in the last 18 months, does not affect humans or dogs, though both can carry the virus and infect cats.

“This is a very unusual strain of the virus,” Jennings said. “Cats were going in a matter of 12 to 24 hours from normal to sick to the point of having to be euthanized.”

Cats brought to the shelter from the Springfield home developed symptoms such as lethargy, sneezing, discharge from the eyes and mouth sores, Jennings said. Vaccines and antibiotics didn’t work, and the shelter’s veterinarians eventually recommended euthanization.

An old ventilation system in the center may have contributed to the spread of the virus, Jennings said.

Euthanizing all affected animals in a shelter is not an uncommon policy, said Scott Giacoppo, a spokesperson for the Washington Humane Society,

“It’s an unfortunate situation, but it’s not the first time we’ve heard of shelters resorting to this,” Giacoppo said.

About six cats were adopted from the shelter since the infected cats arrived, Jennings said, but none of the families have reported infections.

Janet Jacobs, 46, of Springfield, has been charged with four counts of having an unlicensed dog and three counts of inadequate care of animals. Authorities found about 75 cats in her home, Jennings said.

The Fairfax County Animal Shelter is cleaning the rooms that housed cats with bleach and water to eliminate the virus, and cat adoptions have been temporarily halted.

“This has been very devastating for the shelter workers, and we are going to make sure we can accommodate cats safely again,” Jennings said.