All depends on the mitigations people take.
If people think it's serious, they'll take actions to prevent that serious outcome.
If people think it's not serious, then it may become serious.
If people think it's serious, they'll take actions to prevent that serious outcome.
If people think it's not serious, then it may become serious.
Most cases so far have been traced back to people coming back from a vacation trip to Northern Italy and Austria (ski resorts also popular among Italians), but now cases are popping up where health authorities are unable to trace the source of infection, and this, rather than raw numbers, is what has prompted the heightened alert level.