Hi Meriflower: There are certainly sanitary problems reported with greater frequency over recent years (not that they didn't exist before). However, I've looked over the websites listing sanitary issues, and the problems appear to extend to many lines - including Royal Caribbean, Carnival, Celebrity, etc, etc.
The Amsterdam issue occurred in April, and I can only assume that HAL has done everything in its power to rectify the situation. There have been no recent complaints on www.cruisejunkie.com
. which lists incidents on cruise ships.
I encourage you to check out the CruiseJunkie website and list to see that all major cruiselines suffer from sporadic outbreaks of illness.
Careful hand-washing is probably the best prevention against GI illness transmission. If you want to take it a step further, using only bottled water for drinking is another possibility, but I think that's probably excessive.
The Amsterdam is a very lovely ship, and is a nice, smaller size. Leads to a more intimate, yet fun, experience. I'm sure the Noordam is lovely as it's new... but it is bigger, and there's more people about. On a certain level - more people = more likelihood of illness = more likelihood of getting sick
Just a humble epidemiologists opinion. Hope it helps!!