So so sorry to hear about your brother. I do hope that he makes a speedy and complete recover.
Sad to say that Covid, like Norovirus, Influenza, Parainfluenza, Rhinovirus and a host of other illnesses will continue to be with us. In addition, a cruise ship is a “closed circuit” in that if one becomes ill, he or she cannot ‘check out’ and go home.
Make sure that you wash your hands. Make sure that you are up to date with all necessary vaccinations. Take an N 95 or KN 95 makes and make sure that you now how to wear it properly.
Hopefully, the Captain will be on top of any problems and inform the passengers of what measures to take. Make sure that you follow them.