The Royal Canadian Navy is in the midst of a coronavirus-readiness response called Operation Laser.
A Department of National Defence spokesperson said navy crews are being kept quarantined or at sea to remain ready to be deployed.
From CFB Esquimalt, frigate HMCS Regina, with its crew of 225, and the smaller maritime coastal defence vessel HMCS Brandon, with 45 sailors, have been at sea for about two weeks in readiness for the operation.
Two other Pacific-based coastal defence vessels, HMCS Nanaimo and HMCS Whitehorse, are also at sea, ready to be deployed if needed.
HMCS Nanaimo and HMCS Whitehorse returned to Canadian waters this past week. They had been scheduled to remain on deployment until May as part of Operation Caribbe, a multi-nation effort to stop smuggling and drug trafficking.
Both vessels have been at sea now for more than two weeks and neither has reported any cases of COVID-19.
The Pacific frigate HMCS Calgary is also remaining at sea, ready to be deployed if needed on Operation Laser.
HMCS Calgary had been scheduled to sail April 6 for Asian-Pacific waters on Operation Projection. That five- to six-month deployment has been deferred because of the pandemic.