Hel says:
http://www.giantitp.com/comics/oots1081.htmlThanks to my unholy power, every man and woman on that ship is now infected.
Though you are right that the fact they currently have at least three clerics who if they are infected, were infected after they left the airship and so presumably would be symptomatic later greatly lowers the threat. Could be bad news for the airship crew though.