Worth noting that
Italy was the first euro zone country to suspend all direct flights to and from China, provoking the ire of the Beijing government. It took the decision after two Chinese tourists from Wuhan tested positive in Rome in late January.
(paragraph taken from Reuters)
Timeline for context
Flights between Italy and China were stopped on 30th January.
Wuhan was locked down on the 22nd January.
The first patient in the Lombardy cluster had never been to China, but he had been in contact with a friend who had visited there recently.
That man has tested negative for the disease and never had any symptoms. Authorities are trying to establish whether he was a carrier who passed it on.
So the window to stop the spread was much earlier and narrower than realised and there are quite possibly other silent carriers and potential clusters yet to appear.