The recent COVID-19 infection cluster in Zhengzhou, Henan province, was sparked by hospital-acquired infections, and is not related to the outbreak linked to an international airport in Nanjing, Jiangsu province, a health official said on Thursday.

Genome sequencing results of some confirmed local cases at a hospital in Zhengzhou are of the Delta variant and are highly identical to imported cases receiving treatment at the medical institution, Guo Yanhong, an official at the National Health Commission's Bureau of Medical Administration, said during a news briefing.

She said several factors triggered the local outbreak, including a lack of understanding of the complexity and danger of the novel coronavirus mutations, weak supervision over regular disease control work at health institutions, and poor implementation of protocols aimed at curbing hospital-acquired infections.

"The commission has launched a nationwide campaign to stem and prevent hospital-acquired infections," she added.