Australian Wildlife Hospital, Australia (CNN) -- On the operating table lies a sick koala. He's just been brought in by a driver who found the animal sitting in the middle of a busy road. Veterinarian Claude Lacasse determines the koala has not been hit by a car but she immediately detects one serious problem facing many of the marsupials: Chlamydia, a disease which can lead to a very slow and painful death for koalas living in the wild.

Koalas generate almost US$1 billion for the Australian economy, thanks to tourists who come to see this national icon. But these cuddly creatures are under serious threat from infectious disease and habitat loss and some scientists believe they are facing extinction.

"Extinction is inevitable in some areas," according to Dr Jon Hanger, a veterinary scientist at Australia Zoo's Wildlife Hospital. "I certainly hope we don't see it across Australia. But if we don't take the decline seriously and pick up on the warning signs now it's certainly a risk."

A recent report by the Australian Koala Foundation backs up those beliefs. It claims the national population has dropped from 100,000 to fewer than 43,000 in the past six years and if nothing is done to stop the decline, koalas could be extinct within 30 years.

"I can promise you after being on Government committees for years and lobbying minister after minister, I see nothing in our country being done to protect koalas," said Australia Koala Foundation president Deborah Tabart.

"If the Government had grasped this problem 10 years ago, things would be so different. Instead they're on the brink of extinction -- I can promise you that."

Back at the hospital, at least a dozen koalas are in intensive care. Outside, in open-air enclosures, many more are recuperating from disease, dog attacks and encounters with cars. At least 700 koalas are brought here every year for treatment. The majority have Chlamydia, a disease which attacks their eyes and bladder. Most would die in the wild but here at the Wildlife Hospital they receive a two month course of antibiotics and are then returned to their natural habitat -- generally within a kilometer of where they were found.

I was lucky enough to get up close and personal with one of the koalas, recuperating at the Australian Wildlife Hospital. The zoo keepers had named him Tullie, a seven-year-old who was recovering after being hit by a car. He sat in the fork of a tree, surrounded by eucalyptus leaves in one of the outdoor enclosures. The keeper described him as a real "softie" while she gave Tullie his medication.

I stood next to Tullie and patted him. He reached out his paw and touched my hand. The pads of his paw were soft and despite his sharp claws used to climb trees, he was so gentle. He held my hand for a few seconds and did this repeatedly while my piece was filmed for the news story we were shooting.

His nose had deep scratches from the accident and he was also nursing some internal injuries. I was amazed at how peaceful and docile this animal was, even though he was from the wild.

Besides Chlamydia, there is another disease plaguing these marsupials -- and there is no vaccine or cure and it's spreading rapidly.

Koala AIDS or KIDS (Koala Immune Deficiency Syndrome) is similar to AIDS in humans. The immune system of the animals is weakened and they are made susceptible to cancer and other deadly infections.

The hospital's head veterinary scientist, Dr. Jon Hanger, discovered the retro virus causing the condition and says it's just as severe as AIDS in humans but affects koalas more quickly. "It's knocking off a large proportion of koalas that come into this hospital and that means a large number in the bush are dying from it too."

The disease is spread by koalas coming into contact with each other. Hanger believes most of the animals carry the virus, but only some are predisposed to it becoming full-blown KIDS.

"There is no vaccine available now and may never be, but what it's saying to us is that we need to be very careful about the way we manage the population. We have to stop destroying habitat and fragmenting it and we've got to address all the causes of death".

Tabart agrees and says the key factor in the decline of the koala population is loss of habitat.

Land clearing, urbanization and the removal of eucalyptus forests are causing koalas to lose their homes and making them more prone to encounters with cars and dog attacks.

Her slogan "No Tree, No Me," is something she is telling world leaders at the climate change conference in Copenhagen, where she is highlighting this problem as well as talking about how koalas can be part of the solution to lower carbon emissions in Australia through the preservation of their forests.

Her research shows it would take trillions of saplings planted across a land mass three times the size of Australia to replace the carbon stored in the koala forests on the east coast of Australia if they were destroyed by fire or deforestation.

"Without these trees, there will be no koalas. So once again, the beloved koala has the answer to Australia's future," she said.