But now her employers the Red Cross and our own government have gone public in the hope the exposure will bring about the 62-year-old's release.
She and two Syrian drivers, Alaa Rajab and Nabil Bakdounes, were kidnapped at gunpoint, and resigned to a fate unknown.
In a statement, the ICRC said that as recently as December, Akavi may have been seen by at lest two people at a clinic in Sousa, one of the Islamic State group's last outposts.
On Monday, New Zealand Foreign Affairs Minister Winston Peters said his government had worked since 2013 to locate and repatriate Akavi. "This has been a uniquely complex and hard case. It's working with the national staff who do the best they can", she said.
For six years, a shroud of silence surrounded the life of the New Zealander held hostage by Daesh. "That is exactly what we have done here", Peters said.
He said there were Red Cross people on the ground in Syria and Iraq looking for information about Akavi, and he strongly believed she was still alive.
"Personnel have visited Syria from time to time as required". This non-combat team was specifically focused on locating Louisa and identifying opportunities to recover her.
Refugees fleeing the last strongholds of Islamic State report seeing her, still working as a nurse. It is believed she was offered for ransom and may have been used as a human shield.
New Zealand Prime Minister Jacinda Ardern expressed disappointment at the information released by the ICRC and refused to answer questions at her weekly press conference on Monday. But there are hopes her medical skills might have caused her captors to spare her.
For more than five years, Louisa Akavi's identity has been a closely guarded secret.
A spokesman for Akavi's family, Tuaine Robati, said she knew the dangers she faced. "We know she is thinking of us and that she will be anxious about us too".
Akavi had carried out 17 field missions with the ICRC and the New Zealand Red Cross, the statement said.
He said Akavi's family also supported the ICRC's decisions.
"It absolutely remains the government's view that it would be preferable if this case was not in the public domain", she said.
Dominik Stillhart, director of operations for the ICRC, said the organization had chose to permit publication in the hope it would elicit new information on her whereabouts.
"We have not spoken publicly before today because from the moment Louisa and the others were kidnapped, every decision we made was to maximise the chances of winning their freedom". "With Islamic State group having lost the last of its territory, we felt it was now time to speak out".
"Following the fall of the last territory held by Islamic State group, we fear there is an extra risk of losing track of Louisa, though we remain hopeful this period will instead open new opportunities for us to learn more about her whereabouts and well-being", the ICRC said.
He had heard rumours of rescue attempts, and the ICRC network has tried to find her over the last years.