Depends on how you want this to play out It's a simple numbers game.
Small numbers? Barely a ripple. Large numbers? Serious problems.
Lets play catastrophist!
80% of people who get this thing appear to be fine. However, the 20% who aren't will rapidly swamp the health services of all countries affected with ICU beds being the most likely failure point. A mortality rate of 1 - 2% seems to be on the cards with the majority of the dead being old / suffering from other health conditions. It looks like we're going to get a pretty good idea of what happens as the Iranians appear to have gone for the approach of just letting it spread.
I'd suspect the Six Nations will be a casualty but it won't be the biggest. The Olympics is highly unlikely (imho obviously) to proceed in it's current / envisaged form.
The particular problem is lack of testing capability. Without that the Italians really don't know yet what they are dealing with. Risking the health of potentially millions so we can watch a game of rugby seems a bit disproportionate to me.
Just for context there was a lot of worry about swine flu. I got it and it was a miserable experience. But that strain had a mortality of around 0.02% at the moment this thing it appears approximately 100 x more deadly. Spanish Flu had a mortality rate of approximately 2-3% and killed somewhere around 30 million people worldwide.
The name of the game is to buy time and keep numbers low enough for existing capabilities to cope. Our "just in time" ultra connected society is about to find out exactly how resilient such systems are. At this point I'd hope caution wins the day.