Friends and businesses are turning on each other as panic about the spread of coronavirus in Adelaide takes hold.

One restaurant on King William Road has shut down, fearing the son of two customers who dined at their last night could be infected.

The Samurai Teppanyaki House says it is not taking any chances with the health of its customers and staff - immediately closing its doors after a coronavirus scare.

Last night its owners started panicking when they learned two of their customers had a son in isolation, alerting their followers on social media.

He had returned from the United States on March 10 - several days before the federal government made it mandatory for all overseas travellers to quarantine for 14 days.

The restaurant is not taking any chances. Credit: 7NEWS

But the restaurant says his parents should have taken the initiative to stay home too.

“A lot of people are saying we overreacted,” the restaurant’s owners told 7NEWS.

“But you don’t know who’s carrying the virus.”

The couple says their son has shown no signs of illness. Credit: 7NEWS

On Friday the couple, which runs a ballet school on Kensington Road, hit back.

“My son decided to self-isolate to do the right thing,” customer David McMahon said.

“He’s been upstairs on that floor by himself.

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“He’s shown no signs of illness.”

Friday’s federal government ruling that there should be four square metres between patrons could be the final straw for restaurants and bars across Adelaide.

In the video below: PM places restrictions on cafes and restaurants