The death toll from the new virus sweeping across China and surging around the globe closed in on 1,000 Monday amid warnings that the 40,000 known cases may be “the tip of the iceberg.”

Chinese health officials said 97 more deaths were reported Sunday, a spike after days of decline that put the global toll at 910. All but two of the deaths have occurred on the Chinese mainland, most in and around the city of Wuhan.

Total reported cases rose to 40,573, more than 40,000 of them in China. Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, warned that the numbers may not tell the entire story.

“There’ve been some concerning instances of … spread from people with no travel history to China,” Tedros said. “The detection of a small number of cases may indicate more widespread transmission in other countries. In short, we may only be seeing the tip of the iceberg.”