Ellenborough Lewis, a koala rescued from Australia's brushfires, is seen at the Koala Hospital in Port Macquarie, New South Wales, on November 20. Reuters/Nine Network

A story that began with a selfless act and a singular story of survival from the devastating brushfires raging in Australia has ended on a sad note. A woman's dash into the flames to rescue a koala caught in the inferno came too late to save the animal's life.

On Tuesday the Koala Hospital in Port Macquarie said the animal, dubbed Ellenborough Lewis, had sustained burns too bad to recover from, so he was put down.

"We recently posted that 'burns injuries can get worse before they get better'. In Ellenborough Lewis's case, the burns did get worse, and unfortunately would not have gotten better," the Koala Hospital said in a statement posted to their Facebook page. "The Koala Hospital's number one goal is animal welfare, so it was on those grounds that this decision was made."

Today we made the decision to put Ellenborough Lewis to sleep. We placed him under general anaesthesia this morning to... Posted by Koala Hospital Port Macquarie on Monday, November 25, 2019

Australia's annual bushfire season has claimed at least six human lives and destroyed hundreds of homes.

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The woman in the video posted last week removed her shirt and dashed into a wooded area still on fire to pluck Lewis off the ground. She doused the smoldering marsupial with water, wrapped him in her shirt and made sure he got to the Koala Hospital.

More than 300 koalas are feared to have been killed this year. The Koala Hospital even started a GoFundMe account to raise money for the animals' care. The hospital said dozens of koalas have been brought in needing hydration and treatment for burns.

According to the Australian Koala Foundation, it's estimated that around 43,000 koalas still live in the wild in Australia. They're listed as "vulnerable" under the Environmental Protection and Biodiversity Conservation Act.

The bushfires left Sydney covered with smoke last week. BBC News reported that residents were warned about severe fire danger and parts of the city recorded air pollution levels eight times higher than normal.

CBS News weather contributor Jeff Berardelli said rising temperatures due to climate change have left soil and vegetation dried out in Australia, making it more flammable.

"The trend is often towards greater moisture deficits in the atmosphere. Combined drier ground and relatively drier air leads to fires that grow faster and burn longer," he said.