My sister was on your cruise also. She has a sinus infection & was also put on antibiotics. Nothing from the ship though, more from the weather & your own personal immune system.
It's mainly from the storms you guys had at sea, you left NY, it was cold here, hit a storm, went into the tropics where it was hot & then you ran into a storm on the way home with 12+ foot seas.
It's a wonder everyone didn't come down with a cold.
The link below shows the pictures she took of the swells. Look at the album named Norwegian Dawn