People wear face masks in Milan, Italy, Feb. 26, 2020. (Photo by Daniele Mascolo/Xinhua)

Researchers at the Sacco University Hospital in Milan, Italy, announced Thursday they isolated the Italian strain of coronavirus, according to Xinhua news agency.

The strain of the virus from an Italian patient showed genetic differences compared with the original strain isolated in China.

The discovery was made by a team led by professor Claudia Balotta, according to Sacco's Biomedical and Clinical Sciences Department director Massimo Galli.

The new coronavirus may have circulated unnoticed for several weeks in northern Italy before the first cases were detected, Galli said.