The Royal Caribbean cruise ship Quantum of the Seas is berthed at Singapore's Marina Bay Cruise Center on Dec. 9, 2020. A Royal Caribbean cruise returned to Singapore on Wednesday morning after an 83-year-old passenger onboard tested positive for COVID-19, local media reported. (Photos: Xinhua)

A passenger is seen on the Royal Caribbean cruise ship Quantum of the Seas berthed at Singapore's Marina Bay Cruise Center on Dec. 9, 2020. A Royal Caribbean cruise returned to Singapore on Wednesday morning after an 83-year-old passenger onboard tested positive for COVID-19, local media reported.

The Royal Caribbean cruise ship Quantum of the Seas is berthed at Singapore's Marina Bay Cruise Center on Dec. 9, 2020. A Royal Caribbean cruise returned to Singapore on Wednesday morning after an 83-year-old passenger onboard tested positive for COVID-19, local media reported.

The Royal Caribbean cruise ship Quantum of the Seas is berthed at Singapore's Marina Bay Cruise Center on Dec. 9, 2020. A Royal Caribbean cruise returned to Singapore on Wednesday morning after an 83-year-old passenger onboard tested positive for COVID-19, local media reported.

The Royal Caribbean cruise ship Quantum of the Seas is berthed at Singapore's Marina Bay Cruise Center on Dec. 9, 2020. A Royal Caribbean cruise returned to Singapore on Wednesday morning after an 83-year-old passenger onboard tested positive for COVID-19, local media reported.