BEIJING – China said Tuesday that the number of infections from a new virus surpassed 20,000 as medical workers and patients arrived at a new hospital and President Xi Jinping said “we have launched a people’s war of prevention of the epidemic.” Xi presided over a special meeting of the top Communist Party body for the second time since the crisis started, telling the Politburo standing committee on Monday the country must race against time to curb the spread of the virus.