The explanation comes as the health department gets set to adopt a contact tracing program that was adopted by Victoria during its second coronavirus outbreak, which is "being looked at by most governments in Australia".

The Maven Disease Surveillance and Outbreak Management System, from the US, has been described as a system that can help public agencies respond quickly to a communicable disease outbreak.

In response to a question asked during estimates, designed to help people understand contact testing and instill public confidence in coronavirus management, Dr Veitch said efficient contact tracing is a significant factor in reducing transmission from multiple sources.

"There are two broad categories of contacts that we trace. The first are close contacts, so household and work mates, the second are casual contacts," Dr Veitch said.

"The close contacts are those we focus on first of all. There is a critical dependence on speed and effectiveness of that process on the skills and experience of those who do the contact tracing. We were very lucky to have good contact tracing in place [arising from meningococcal tracing experience] ...if you got a case in the late afternoon, they would usually have made contact with a case and identified all of their close contacts by later that evening."

He said there were 11 contact tracers initially, arising from the communicable diseases unit, and that a number of other people including experienced public health nurses, were brought in throughout the initial outbreak.

"Casual contacts are the more remote contacts. We initially tried to contact all casual contacts then mid way through the epidemic, about April and May, there was a stepping back where we no longer tried to pursue casual contacts and just put out a notice.

"But we have swung back in the other direction [now] where we do try and make contact with the casual contacts, that reflects a desire for prevention."

Dr Veitch said getting personal contact information from individuals who visit hospitality and other venues was important to this task.

He said that while not all venues are recording that information and not all people are leaving their details, the information that was otherwise being collected did assist contact tracers in their task.

Health minister Sarah Courtney said individual responsibility to provide information was key.

"There is a careful balance between making sure that everyone has confidence in the system, but through having that confidence we don't have complacency in the community, and that people have personal responsibility through this process."

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