The last time the vessel had passengers was March 14, 2020, before the Coronavirus (COVID-19) pandemic exploded in the USA. Ever since ~800 staff-crew (from 100 different nationalities) remain stranded at sea.
HAL (subsidiary of Carnival Corporation) hoped for a crew debarkation in LA, but the CDC didn't permit the operation.
The US Government ordered all cruise companies to suspend passenger shipping operations in mid-March 2020. According to Melinda Mann (HAL's youth program manager) after that, they had discovered they "had one sick person onboard a few weeks later.” That had been around the beginning of April and she had been quarantined, and then medically evacuated (via tender boat) in Cabo San Lucas (Baja Mexico).
That sick passenger led to quarantine for the entire crew, which has been floating in international waters for over a month. MS Oosterdam is currently heading to Ensenada (Mexico) with a new crew debarkation plan.
On Tuesday, Holland America released a statement that said:
“No crew were permitted to disembark from Oosterdam today. We continue to work with the US Centers for Disease Control and Prevention (CDC) to obtain approval to disembark crew in the U.S. for immediate return home under their current no sail order which does not allow us to do so at this time, including for U.S. citizens.”
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.