The former Launceston teacher disappeared while walking with his wife, Louise Fairfax, in southern bushland on Saturday.

The couple were on the Duckhole Lake track together but Mrs Fairfax was just ahead of her husband taking photos – she has not seen him since.

The distressed wife and her two daughters have spent every day helping emergency crews search for the 66-year-old, who has Parkinson’s disease.

He has now been without his medication for nearly a week and police said he was on the “edge of surviving”.

The search has involved more than 60 people, including Tasmania Police officers, SES rescue personnel and community volunteers as well as Ambulance Tasmania who have been on site keeping an eye on the crew.

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The volunteers have included staff and students from Launceston Church Grammar School where Mr Fairfax was a teacher until last year.

Inspector David Wiss has been coordinating the search operation from the police forward command post, which was setup on the track where Mr Fairfax was last seen.

Inspector Wiss said the support of volunteers had been “overwhelming” over the past five days.

“Tasmania Police would like to thank the overwhelming number of volunteers who have come forward to help … they have done a fantastic job,” he said.

The search became more targeted on Wednesday as police focused on using “specialist resources”.

But Mr Fairfax was still missing on Wednesday night.

Messages continue to be shared from across the state in support of him and his family.

“Thinking of all of you - you're a strong family so hoping for a good outcome,” Ceri Weeks said.

“I hope they find Bruce, such a humble man and a great teacher. Someone who had the respect of a whole school,” Zach Whelan said. 

Labor senator Helen Polley said Mr Fairfax was a “highly respected teacher”.

“My heart goes out to the family, we await good news,” she said.

Thursday will be the sixth day of the search.