The AFL season is hanging by a thread after the South Australia government announced it is closing the state’s borders from 4pm on Tuesday.

People arriving after that time will have to self-isolate for 14 days which means the Adelaide Crows and Port Adelaide could not host teams or return home from away games and keep playing.

Prime Minister Scott Morrison has also recommended all non-essential travel be cancelled, with both developments throwing the entire AFL season into disarray.

However, football teams could be granted exemptions to continue entering South Australia as normal.

The state government said essential transport includes transport for health and medical supplies, health personnel and patients, food and commercial supply chains, near-border interactions, travel of a relative or carer of a dependant, and emergency services.

In addition, fly-in-fly-out mining workers or national-level sporting teams could be exempt “provided they had approved disease control mechanisms in place”.

The SA government’s advice leaves a decision on the AFL season squarely in the league’s hands once again.

“I’m ordering the effective closure of our borders to protect the health of South Australians by slowing the spread of the virus,” SA Premier Steven Marshall said.

“The health of South Australians is unquestionably our number one priority and that is why we are acting swiftly and decisively to protect them from the impact of the disease.”

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The AFL hosted its opening round in empty stadiums this weekend and is one of the last sporting competitions in the world still playing.

The Crows and Port face each other in round two so the league could technically continue unaffected for another week but it looks increasingly likely to be suspended.

AFL boss Gillon McLachlan could be forced to suspend the season. Credit: Getty

7NEWS reporter Mark Stevens believes it is “inevitable” the AFL will be shutdown.

“Genuine confusion around AFL being essential or non-essential travel ... one leading footy official just replied “who knows?”. Awaiting more clarity from league,” Stevens said.

“We’re clinging on to footy, and bravo to AFL for doing everything possible to get it started, but it now looks inevitable we’re going to have to let it go. Murmurs now these three games today the last we’ll get for a while.”

7NEWS AFL reporter Tom Browne also believes the season is in “serious doubt”.

“The AFL season unfortunately for the moment is in serious doubt. The states are considering border controls. And, just to clarify, it’s very unclear whether footy is ‘essential’ travel in any case.”