He said monthly testing had been done since 2003 and all results had been negative.
The testing had been stopped in April after the building was upgraded, and Boreham said the building was fully compliant.
He said the ill woman was still working and expecting results within a few weeks to confirm whether it was legionnaires disease.
In 2003, 14 staff members contracted the potentially fatal illness. The building was vacant for months and staff received confidential payouts.
The Police Association criticised management handling at the time of the 2003 outbreak, saying senior officers denied the problem and positive test results were withheld from staff.
Police Association president Greg O'Connor yesterday said staff were looking for reassurance after police were slow to act during the last outbreak.
"That's [the association's] job basically, to make sure it's not a repeat of 2003. This time we are very much satisfied that there has been a change in attitude by the police."
Police Minister Anne Tolley said police were taking the situation extremely seriously, though nothing has been confirmed.
"I would expect police to take all possible precautions to ensure the safety of staff," she said. "Significant resourcing has been invested in this building, and we recently announced the completion of a $7 million revamp, and I'm advised that air conditioning and cooling tower systems have also been replaced."
Boreham said the building had been extensively modified since 2003.
Former building manager Hope Crewther said she was appalled the testing had stopped.
"I said, 'you can't stop that testing — that was an agreement with the Police Association'."
Legionnaires disease is a form of bacterial pneumonia first identified after an outbreak at an American Legion meeting in 1976. It is spread chiefly by water droplets through air conditioning systems.