The competition was suspended in March due to Covid-19 and the 24-year-old Dunedin rider returned home to wait for the all-clear.
It will resume in Mantova, Italy, this weekend.
There is also a midweek meeting.
Duncan is nursing a slim series lead.
She is on top of the standings with 90 points.
German rider Larissa Papenmeier is second on 85 points, while six-time world champion Kiara Fontanesi, of Italy, is third on 80 points.
But there is a maximum of 100 points up for grabs in the four races this week.
The series will conclude in November with a final meet.
Duncan left for her base in England earlier this month and, upon her arrival, would have set to work familiarising herself with her new bike.
Kawasaki has upgraded to the 2021 model and it is a quite a different set-up from what she is used to.
It has an electric start which will help ease the nerves. The previous bike could be temperamental.
There is also a hydraulic clutch and a new chassis. But Duncan told the Otago Daily Times before she left she was confident she would have ample time to get used to the new bike before race day.
"I have no hesitation. It will be a good bike," she said.
