A rare bacterial strain killed three tufted puffins at Point Defiance Zoo & Aquarium beginning in late June.

Crews in protective gear are collecting samples across Point Defiance Park to trace the source.

The zoo said in a Sept. 15 news release that further testing identified the bacterium as a rare avian strain of Chlamydia abortus. Initial results in July had pointed to Chlamydia psittaci, the more common bug behind parrot fever.

The distinction matters. Avian Chlamydia abortus can infect humans, but documented human cases are so rare that routes of infection remain unconfirmed, the release said. No human cases have been linked to the puffin deaths.

The three tufted puffins died beginning June 23, The News Tribune first reported in July. The puffin habitat has been closed since late June. All remaining birds were put on antibiotics, and animal-care staff began wearing enhanced protective equipment.

No additional birds have been identified as infected since July. Environmental testing inside the habitat in early August did not detect the bacteria.

The exhibit houses 33 tufted puffins, six horned puffins and five common murres, zoo spokesperson Tessa Miller told The News Tribune.

"This is an unusual finding, and we are working to learn as much as we can about where this strain may have come from," Dr. James Miller, health officer at Tacoma-Pierce County Health Department, said in the release.

How the bacteria entered the habitat is still unknown. Exposure from a wild bird is one possibility, the zoo said.

Representatives from Washington Department of Fish and Wildlife, the zoo, Tacoma-Pierce County Health Department and Washington State Department of Health are collecting environmental samples in Point Defiance Park, the zoo announced Sept. 15.

The protective equipment visitors may see on those workers is a precaution for staff handlthree tufted puffining bird feces, not a sign of broader public risk, the release said.

Dr. Karen Wolf, the zoo's head veterinarian, said the puffin habitat will reopen once veterinary and public health officials determine it is safe. No timeline has been announced.

Samples are being sent to the University of Georgia Infectious Diseases Laboratory, which specializes in Chlamydia bacteria in animals and wildlife. The zoo is also coordinating with Parks Tacoma, the state Department of Agriculture and the Centers for Disease Control and Prevention.

Point Defiance Park and the rest of the zoo remain open to the public.