By Roxanne Liu and Ryan Woo BEIJING (Reuters) – Multiple Chinese cities are adopting fresh COVID-19 curbs, from business halts to lockdowns, to rein in new infections, with the commercial hub of Shanghai bracing for another mass testing campaign after detecting the BA.5 Omicron subvariant. As China sticks to its “dynamic zero-COVID” policy of promptly stamping out all outbreaks, the strict curbs by local governments come despite low caseloads, at a time when much of the world co-exists with the virus. The central government has said curbs must be as targeted as possible to reduce damage to the…