BEIJING—Three pet cats that tested positive for coronavirus were put down in the northeastern Chinese city of Harbin, state-backed media reported, leading to a social media backlash at what some viewed as overkill in local efforts to contain the virus. The owner of the cats was diagnosed with COVID-19 on Sept. 21 and the local disease control agency euthanized her three cats, which also tested positive later, despite her objections, Beijing News reported late on Tuesday. “There is probably no professional medical treatment for animals infected with the novel coronavirus,” a community worker said in an interview with Beijing News, explaining why the cats were killed. The community worker said the cats would have continued to leave viral traces in the room. “It doesn’t seem very realistic that the cats would contaminate the environment so badly that they would be a risk for their owner to re-contract COVID,” said Rachael …