Every cat in the Fairfax County Animal Shelter was euthanized Wednesday night to contain the spread of a highly contagious virus, Fairfax County police said Thursday. 

Several cats infected with a virulent strain of Calicivirus, which causes upper respiratory distress, were brought to the animal shelter earlier in June, police said.

Over the next week, other cats exposed to the virus began exhibiting symptoms such as lethargy, sneezing, discharge from the eyes, and mouth sores.

Available vaccines and antibiotics were ineffective, police said, and euthanizing sick and exposed cats did not stop the spread of infection.

The shelter's veterinarians then recommended euthanizing all cats in the shelter following national shelter protocol, police said. It was not immediately clear how many cats were euthanized.

Cat adoptions have been temporarily halted, police said, and the shelter is cleaning the rooms used to house cats.

The virus does not affect humans or dogs, though dogs can carry it on their coats and infect cats in the same area. 

Dogs are still available for adoption at the shelter.

Cat owners who suspect their cats may be infected are encouraged to seek treatment, police said.