The illness seems to have subsided. After the 14 day contagion period, once the crew have become immune / quarantined it was about 7 days for it to disperse from them. According to the CDC they are at code yellow. They should have quarantined the ship the first cruise (3/7) but celeb was more interested in revenue.
Mid may sailings should be fine, especially to alaska. Some of the problems come from people eating bad food onshore (or drinking mexican h2o) and not washing their hands. Hand sanitizers don't kill norovirus, washing hands thoroughly does.
As far as vibration problems, deck 9 is pretty high up, you should be OK. It's when you are right over the bow or stern thrusters that you have issues. Deck 4-5-6 in the back it would be pretty loud.