Thursday night's match at the Stadio San Paolo in Naples will be played at an unknown date in the future, said a statement from the tournament organisers Lega Serie A.
Serie A said that it had followed orders from the prefect of Naples calling for the delay of the tie which Napoli lead 1-0.
The semi-final second leg between Juventus and AC Milan in Turin on Wednesday has also been postponed over concerns about coronavirus which has caused 79 deaths and infected more than 2,000 people in Italy
Outburst
Inter Milan's Serie A clash at Juventus last weekend was postponed even though it was due to be played behind closed doors.
The sudden move prompted the Inter chairman Steven Zhang to launch a furious verbal assault on social media on the Italian football league boss Paolo Dal Pino. Zhang branded Dal Pino a clown for the apparent randomness of the decisions to postpone or play matches.
Sports events have been banned in three Italian regions - Lombardy, Veneto and Emilia Romagna - plus two provinces.
Only four Serie A matches took place last weekend, while the entire Swiss top flight has been suspended until 23 March.
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