A piggery at Dunedoo in Central West NSW remains in lockdown after pigs at the property tested positive for the illness.

It is believed that a sick farm worker transmitted the virus to the pigs, reports ABC.

Andrew Spencer, from Australian Pork Limited, says people infected with swine flu pose a serious threat to the industry.

"We've got producers who've sent sick workers to the doctor and were keen to find out if they had the swine flu variant of human influenza," he says.

"But they haven't been able to tell that, because doctors aren't allowed to just run routine testing for it.

"We're actually in discussions with the Department of Health about that."