I just thought it was kinda unusual as I haven't had any sick villagers before the Welcome Amiibo update, so if anyone knows the answer to my question please tell me
From what I've heard they do get sick but much more rarely. There was a thread about it a while ago, where this Topic was discussed Maybe search for it in the Forum?
From my personal experience:
Before the update I had villagers getting sick at least once a week. After the update it didnt even occure once!
Since the update, I haven't had any ill villagers and I have twenty towns. If it is rare that they still fall ill, it must be extremely rare. That said, I see the rare red train go through town quite often
I don't think it does happen at all. No one I know has ever mentioned the villager's getting sick after the update. Whether it was a coding mistake or they've had too many people whining, we will never know. I personally thought it brought some more variety to the game to be honest, if it was due to complainers.