China has denied covering up human bird flu cases after a US-based newspaper said local officials may be hiding suspected infections from the central government and that the country's death toll could be higher than the 12 reported. "We must clarify that China has not been concealing any confirmed or suspected human case of bird flu since the first case occurred in November of last year," Ministry of Health spokesman Mao Qun'an said in an interview with the official Xinhua News Agency published late Friday. It was a rare official response to reports by foreign media. The Wall Street Journal, citing an unnamed source, said Thursday that local Chinese health officials "have failed to report possible human cases of bird flu to the central government," raising concerns that more people than reported may have contracted the disease. China has reported 18 cases, including 12 deaths.