Nearly 3,000 sailors aboard a US Navy aircraft carrier will be brought onto the tiny Pacific island of Guam, as they struggle to quarantine crew members in the face of a coronavirus outbreak.

Key points: Naval vessels pose major risks for the spread of COVID-19 due to their close quarters

Naval vessels pose major risks for the spread of COVID-19 due to their close quarters Around 1,000 sailors have already gone ashore in Guam, with more to disembark

Around 1,000 sailors have already gone ashore in Guam, with more to disembark The Roosevelt could be out of duty in Guam for several weeks as people are quarantined

There are 5,000 crew on the USS Theodore Roosevelt and the number of sailors who have tested positive for COVID-19 is nearing 100. Nobody on board is reported to have died.

Those who have tested negative will be brought onto military bases and local hotels for quarantine, with a "no contact policy" between sailors and the local community.

Guam, a US territory, is facing its own coronavirus emergency.

The island has only 250 staffed hospital beds and has among the most cases in the Pacific with 77 confirmed infections and three deaths.

US officials are working with the local government on Guam to find suitable accommodation. ( ABC News: Greg Nelson )

Sailors getting off the carrier deemed 'a necessary risk'

Navy Captain Brett Crozier, the carrier's commander, raised warnings this week in a memo to his leaders in which he asked permission to isolate the bulk of his crew members on shore.

The carrier, like other Navy ships, is vulnerable to infectious disease spread given its close quarters.

Most sailors share rooms with multiple people, work in close proximity to others, routinely grab their food from crowded buffet lines and eat at tables joined end to end.

Captain Crozier said the spread of the disease was accelerating and that removing all but 10 per cent of the crew would be a "necessary risk" to stop the spread of the virus.

"We are not at war. Sailors do not need to die," he said.

"If we do not act now, we are failing to properly take care of our most trusted asset — our sailors."

Navy leaders were quick to praise the captain for bringing the dire nature of the matter to their attention. They brushed away suggestions that he could be punished because the issue became public so quickly.

The President of Guam's Medical Association, Thomas Shieh told ABC Radio Australia's Pacific Beat that he was confident they can keep the local population as well as the sailors safe.

"These are healthy sailors so I'm not too concerned regarding the healthcare status," he said.

It is unclear where COVID-19 cases aboard the USS Theodore Roosevelt originated. ( Supplied: US Navy )

But some sailors will remain onboard to perform essential tasks.

"This is a battleship … that has nuclear power … it's very different to a cruise liner," Dr Shieh said.

"They're going to have to keep some people on board to maintain the battle-readiness."

Acting Navy secretary Thomas Modly made it clear that while several thousand will leave the ship, other sailors will remain on board in order to continue to protect the ship and run critical systems.

"We cannot and will not remove all sailors from the ship," Mr Modly told Pentagon reporters.

He said officials will send as many sailors off the ship as possible while still maintaining safety. About 1,000 have already gone ashore, and that number will grow to at least 2,700 in a couple of days.

If crew members are required to be quarantined for 14 days, on a rotational basis, the Roosevelt could be out of duty for weeks.

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Origin of the outbreak remains unclear

Navy leaders said that they are trying to track down any sailors who came in contact with those now ill and place them in quarantine.

They said almost 1,300 sailors have been tested and nearly 600 of those tests came back negative. Officials are awaiting more results and more testing.

Most of the USS Theodore Roosevelt's sailors are likely to come onto land for quarantine. ( AP )

Navy leaders have faced persistent questions about the origin of the virus on the ship but said it may be impossible to identify where it started.

The Roosevelt made a port call in Vietnam last month.

Mr Modly said the stop, where thousands of sailors likely went off the ship into Danang, was done when there were fewer than 20 cases of the illness in Hanoi and sailors were screened when they returned to the ship.

He said two sailors fell ill near the end of the required 14-day period between port calls, and they were flown off the ship. As the days went by, however, the problem worsened.

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