Passengers on the cruise ship MSC Preziosa had to wait more than six hours to disembark at Rio de Janeiro Sunday due to an inspection by Brazilian health authorities that confirmed 28 cases of COVID-19 on board - 26 passengers and two crew members.

Rio’s health secretariat said in a statement that among those who tested positive, people living in Rio or the nearby region can quarantine themselves at home. Others must first isolate in hotels, and there was no information provided about who would pay for the costs.

After the inspection, MSC Preziosa was authorized by federal health regulator Anvisa to continue operating. Other passengers were waiting to embark for Bahia The ship had set out from the Brazilian island of Búzios.

The Associated Press tried to contact MSC to ask about the health measures taken - this is the company’s third ship with confirmed COVID-19 cases over the past year - but didn't receive a response. Authorities did not say how many people were aboard the MSC Preziosa or what nationalities they were.

Epidemiologist Denise Garrett, who is also vice president of Brazil's Sabin Vaccine Institute, said the atmosphere on cruise ships “very conducive to transmission, especially now with omicron.”

“There are thousands of people sharing the same indoor air," she said. "It should be avoided at all costs.”

The U.S. Centers for Disease Control and Prevention last week raised the risk of COVID-19 spreading on cruises to the maximum level, saying COVID-19 can spread easily among people on board, even among those fully vaccinated.

Anvisa has issued a recommendation to Brazil's health ministry that the travel season be suspended. The ministry said in a note it “will evaluate the appropriate measures together with the ministries related to the issue.”