"Lewis" the koala, who was brought to international attention by a viral video of him being rescued from Australia's devastating bushfires, has been euthanised.

Port Macquarie Koala Hospital made the sad announcement yesterday on Facebook, stating that they had placed him under general anaesthetic that morning "to assess his burns injuries [sic] and change the bandages."

"We recently posted that 'burns injuries can get worse before they get better'," wrote the hospital. "In Ellenborough Lewis's case, the burns did get worse, and unfortunately would not have gotten better.

"The Koala Hospital's number one goal is animal welfare, so it was on those grounds that this decision was made. We thank you for your ongoing support."

Named for his rescuer Toni Doherty's grandchild, Lewis was found on November 19 in bushland along New South Wales' Oxley Highway, west of Wauchope. Doherty told 9 News two days later that Lewis had left the hospital and was being looked after by a carer, though a hospital spokesperson only gave the koala a 50 percent chance of survival.

Unfortunately it seems his health deteriorated after that, and the hospital was forced to make the difficult decision to put him to sleep. He was 14 years old.

Speaking to Mashable via email, Port Macquarie Koala Hospital's Sue Ashton said the hospital has treated 33 koalas for bushfire-related injuries since the fires began, with three having been euthanised. They believe many more have died without receiving care.

"In the Port Macquarie region we know up to 350 koalas perished in two weeks," said Ashton. "However this is a very conservative number; we think there are a lot more."

"We think the fires have wiped out many wild koala populations with many being incinerated, and burnt to ash. Koalas' gestation is 35 days, and fertile females breed about every 18 months to two years. It will take decades for the wild koala population on the east coast of Australia to recover."

This will be made much harder by the omnipresent threat koalas already face from changes in Australia's climate. Speaking to Mashable previously, Currumbin Wildlife Hospital's Dr Michael Pyne said the heat and lack of rain has resulted in less plant life, causing koalas and other native wildlife to die of starvation and dehydration.

"Those that escape the fires, that manage to flee, that manage to move on, they're putting even more strain on an already really struggling habitat that's not sustaining what was there," said Dr Pyne.

Port Macquarie Koala Hospital launched a GoFundMe last October to help address this issue, hoping to raise $25,000 for wildlife drinking stations in burnt out areas. It has now raised almost $1.75 million — 70 times their initial goal.

As a result of this outpouring, the donations will now also finance the establishment of a wild koala breeding program. Ashton states that this program has been brought forward five years, and that they "are hopeful this program ... will rebuild the koala populations decimated by the bushfires."

Australia's bushfires continue to rage across multiple states uncontrolled, and are expected to do so for months. Six people have been confirmed dead and hundreds of homes destroyed, with 2.5 million acres burned in NSW alone.