The Eintracht Frankfurt striker scored twice in the opening 23 minutes before Blerim Dzemaili made it 3-0 against Group E's whipping boys before the break in Serravalle.
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Seferovic opened his account with a 10th-minute header following a cross from former Fulham winger Pajtim Kasami.
Kasmi hit the crossbar two minutes prior to Seferovic's second - a powerful left-footed shot into the bottom corner.
Galatasaray midfielder Dzemaili increased the away side's advantage further on the half-hour mark when he rose to nod home the delivery of full-back Ricardo Rodriguez, who had got to the left byline.
Switzerland, who are ranked 10th in the world, lost to England and Slovenia in their first two qualifying games.