The victory leaves Wales just one win away from a fourth Grand Slam in 13 years.
They travel to face France on the final weekend, though Les Bleus – in action against England at Twickenham later on Saturday – still have their postponed contest against Scotland to fit in also following a Covid-19 outbreak.
Listless Italy – who were not helped by an early yellow card for captain Luca Bigi – remain without a Six Nations win since 2015.
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