The Victorian Department of Health said it had conducted a thorough investigation and was following up with selected patients who had contact with the worker in the unnamed region.
"This is entirely precautionary as there are no reports of any patient contracting HIV from the health care worker," it said in a statement.
"But we are erring on the side of caution and recommending a blood test to rule out the presence of HIV."
One woman, who spoke on public radio without giving her full name, said she had felt "very sick in the stomach" after receiving a letter from the health department urging her to have a test.
"I don't know where I (may have) got it because it's all very secret at the moment," she said.
Authorities said the chances of infection passing from the health care worker to a patient were very low.
"As I understand it the latest numbers are, of the 399, contact has been made with 248, 88 have had tests and all of those tests have been negative," state Health Minister David Davis told reporters.
Officials cannot name the health worker or the procedures they were involved in or where they took place.
"What I can say is a health professional was detected with HIV, they have ceased practising," Davis said.
HIV is a blood-borne virus spread through unsafe sex with an infected person and blood-to-blood incidents such as needle stick injuries.