Chief Public Health Officer Nicola Spurrier said the man was in a stable condition and was isolating at home.
She said no close contacts had been identified in SA so there was no risk to the wider community.
"This is somebody who has picked up the infection overseas, has seen the travel advice, got diagnosed and is stable and there is no further risk to us," Professor Spurrier said on Thursday.
"We don't expect this to be spreading widely."
Symptoms of the virus, which has broken out internationally in recent weeks, include fever, chills, muscle aches, swollen lymph nodes and exhaustion.
The disease is endemic in Central and West Africa and is usually spread through contact with animals or consumption of wild game.
Professor Spurrier said a public health alert would be sent to GPs across the state to remind them to watch out for cases of the virus.
So far about there have been about a dozen infections reported across Australia.
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