Officials in a Chinese city on the border with North Korea say they can’t figure out where persistent new Covid-19 infections are coming from — and suspect the wind blowing in from their secretive neighbor. Despite being locked down since the end of April, daily cases have been trending up in Dandong, a city of 2.19 million. Most of the infected people found in the community during the past week hadn’t been outside of their housing compounds for at least four days prior to their diagnosis, according to the city’s Center for Disease Control. While the virus is flaring elsewhere in China, including in its northern regions, officials say they’re unable to establish a chain of transmission. Their suspicions have instead settled northward, with […]