Western Australia is the latest state to shut its border to South Australia, which will return to restrictions from tomorrow as the state scrambles to contain an outbreak linked to hotel quarantine.

South Australia has announced all inbound international flights will be suspended, people will be asked to work from home, gyms will be shut and community sport cancelled.

Home gatherings will also be restricted to 10 people, funerals capped at 50 people and hospitality venues will have to limit patron numbers under restrictions that will be reintroduced from midnight on Monday.

South Australian Premier Steven Marshall has accepted an offer of extra help for Australian Defence Forces to help with the outbreak which has grown to 17 cases.

"We will throw absolutely everything at this to get on top of this cluster,'' Mr Marshall said.

South Australian Chief Health Officer Nicola Spurrier warned the state was facing a second wave and testing, contact tracing and quarantine had been ramped up in the wake of the cluster.

Both Mr Marshall and Professor Spurrier stood by the state's hotel quarantine system, trying to avoid comparisons to Victoria's disastrous system which led to the state's second wave.

"The hotel quarantine system in South Australia is as good as anywhere in Australia," he said.

"As has already been indicated, we have been visited by other jurisdictions who have asked how we've done it. We've also been independently reviewed and we've passed with flying colours."

The outbreak saw WA slam its borders shut less than two days after reopening them to South Australia. The border closure will come into effect from 6pm and anyone travelling from SA to WA will have to quarantine for two weeks.

Queensland, Tasmania and the Northern Territory have also closed borders with SA.