Carnival Mardi Gras made an unexpected stop after crew members spotted a distress flag at sea.

In unvaccinated patients, the highly-spreadable virus can lead to pneumonia, ear infections, fever, a red-colored rash and brain swelling known as encephalitis. Measles is less common on cruise ships, but it can linger for hours after an infected person leaves the room.

From wildlife viewing in the remote polar regions to magical sunsets in the South Pacific, these ships offer unforgettable voyages.