BEIJING (AP) Anti-virus controls that have shut down some of Chinas biggest cities and fueled public irritation are spreading as infections rise, hurting a weak economy and prompting warnings of possible global shockwaves.

Shanghai is easing rules that confined most of its 25 million people to their homes after complaints they had trouble getting food. But most of its businesses still are closed. Access to Guangzhou, an industrial center of 19 million people near Hong Kong, was suspended this week. Other cities are cutting off access or closing factories and schools.

Spring planting by Chinese farmers who feed 1.4 billion people might be disrupted, Nomura economists warned Thursday. That could boost demand for imported wheat and other food, pushing up already high global prices.

The closures are an embarrassment to the ruling Communist Party and a setback for official efforts to shore up slumping growth in the worlds second-largest economy. They come during a sensitive year when President Xi Jinping is expected to try to break with tradition and award himself a third five-year term as leader.