Dr. Eilish Cleary, the province's high-profile chief medical officer of health, is not on the job and no one will say why.

Cleary has been on leave for several weeks, CBC News has learned.

Cleary confirmed by email she is on leave, but turned down a request for a comment. She referred CBC News to the human resources office at the Department of Health.

"As you know we cannot comment on personnel matters," said health department spokesman Bruce Macfarlane. "However, I can confirm Dr. Jennifer Russell is currently serving as acting chief medical officer of health."

Cleary oversees public health programs in the province, from routine flu-shot awareness to the large-scale swine flu immunization effort in 2009.

She has also taken two extended leaves of absence, one in late 2014 and one earlier this year, to work with the World Health Organization on the Ebola epidemic in West Africa.

Cleary has been outspoken about several high-profile public health and policy issues, including what she called the "social and community health risks" of shale gas development in New Brunswick. Shale gas was the centrepiece of the previous Progressive Conservative government's job creation strategy.

In 2012, the Tories said they might not let her release her report to to the public, but then relented.

The Liberals accused the PCs of trying to "muzzle" Cleary, and in their 2014 election platform they committed to "ensuring the independence of the medical officers of health."

It's not clear whether Cleary asked for the current leave or whether the department put her on leave.