SHIJIAZHUANG, Jan. 10 (Xinhua) -- The "patient zero" of this round of COVID-19 outbreak in north China's Hebei Province may have been infected before Dec. 15, 2020, local health authorities said Sunday.

The conclusion is based on preliminary results of epidemiological investigations, said Shi Jian with the provincial center for disease prevention and control at a press conference.

After conducting gene sequencing on the positive samples, the center found that the virus strain is from Europe, but is different from the variants recently discovered in Britain or South Africa, Shi said, adding that the work to trace the "zero patient" is still underway.