The four were admitted to a hospital in the Tuscan port of Livorno Sunday at the end of a cruise by MSC's Orchestra liner, Italy's ANSA news agency reported.
Two crew members were in the hospital's intensive care unit -- a 32-year-old Indonesian, who was critically ill, and a 47-year-old Italian man.
The two other sick crew members were in the hospital's infectious diseases unit.
The ship left Livorno to start another cruise late Sunday.
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