Only you know your risk tolerance. Personally, I would still go unless it gets significantly worse in Switzerland. I'd be monitoring conditions for the next couple of weeks, and it's good you are able to change plans at the last minute.

Also realize that at some point the decision may not be yours to make. Airlines are reducing flights and canceling some destinations. Some hotels and restaurants may close or have restrictions. As I'm sure you've seen in NY, we are seeing areas quarantined in the US and Italy. You may even find you get there and then aren't able to stick to the itinerary you planned. To me, it's much more about a disruption of the trip than a concern about catching the virus.

I'm guessing it will go the way of SARS and Avian flu, etc. eventually, but doesn't seem like that will be in 5 weeks.