It says on its website the ship is a religious retreat at the pinnacle of a Scientologist's spiritual journey.
"Quarantine is a word that people respond to very strongly, but it's actually one of the strongest tools in the public health tool kit", Katz said. Church officials have not returned messages for comment.
Detained passengers were pictured on the deck of the vessel in this picture during its mooring at St. Lucia earlier this week. A blood sample was taken and sent to nearby Aruba, where officials confirmed it was measles on April 29, a day after the ship had departed for St. Lucia.
"The confirmed case as well as other crew members are presently stable, but remain under surveillance by the ship's doctor", she said, noting the incubation period of measles is 10 to 12 days before symptoms appear.
There were about 300 people aboard the ship, according to Saint Lucia authorities, which said they provided 100 doses of measles vaccine at no cost. The ship has now turned back to Curacao. Symptoms may include fever, cough, runny nose, watery eyes and a rash of red spots. The measles virus is highly contagious and can cause blindness, deafness, brain damage or death.
Measles has sickened more than 700 people in 22 US states this year, with federal officials saying the resurgence is driven by misinformation about vaccines.
Diagnoses are at their highest levels since 1994, when 963 cases were reported.
Some of them triggered U.S. outbreaks, mostly among non-vaccinated people. NY has been one epicenter of the outbreak, where there have been 493 cases this year. If they have already caught the disease, the vaccine should reduce the severity.