Whole-genome sequencing has pointed to a young woman who flew back from the United States is the source to cause more than 80 people infected of novel coronavirus in Harbin, Northeast China's Heilongjiang province.

As of April 27 at midnight, 89 people were infected of novel coronavirus in the latest wave which began April 9, according to a news conference of the Heilongjiang provincial government on Tuesday.

The whole-genome sequencing of samples from 21 persons showed 18 persons were infected with the same virus, and only one or two nucleotides were different on the other three, said Zhang Xue, president of Harbin Medical University, at the conference.

Zhang, also an academician at the Chinese Academy of Engineering, said the results also showed the genome sequence in the latest wave in Harbin is distinct from those tested from other Chinese groups.

He said the whole-genome sequencing results supported that the local outbreak's origin was from overseas, and evidence of epidemiological investigation pointed to Han as the source of the spread.

Han, 22 years old, flew back to Harbin on March 19 and was in quarantine at her apartment until April 3. She then flew to Shanghai for cosmetic surgery.

From beginning to end, Han exhibited no symptoms and several rounds of nucleic acid testing during her quarantine showed she was not infected.

On April 9, a local resident surnamed Guo became the first confirmed case of the latest wave in Harbin, and Guo's close contact was Cao, who lived upstairs in the same building with Han.

A later test on Han showed IgG antibodies were present, which means she was infected in the past.

According to the Harbin health commission, Cao's family members and friends had frequent family and dining gatherings, including one that brought seven people together on March 29.

An 87-year-old male confirmed case, a close contact of one of Cao's family members, received treatment for a cerebral stroke at two hospitals in Harbin between April 2 and 8, causing several patients and their family members in the same ward to become infected.