The quarantined cruisers will be tested by CDC personnel (US Centers for Disease Control). The passengers (all Chinese nationals) started exhibiting Coronavirus symptoms on the vessel en-route to NYC back from The Bahamas. A federal official said there was no indication any of the passengers actually had Coronavirus, and that those steps were being taken out of an abundance of caution.
In a statement, Royal Caribbean announced:
"We are participating in elevated levels of guest screening to check the spread of coronavirus. We are closely monitoring developments regarding coronavirus and have rigorous medical protocols in place onboard our ships."
For other Anthem of the Seas accidents and incidents see at the ship's CruiseMinus page.
For Coronavirus updates on cruise ship quarantines (infected passengers and crew) and top-pandemic countries (COVID-19 cases and deaths, daily updated statistics) see at CruiseMapper's Norovirus page.