(Video APTN)

A hundred years ago, Australia's native koala was hunted to near extinction in some regions by fur traders seeking its soft, gray pelt.

Since then, the cuddly looking marsupial has won protected status and bounced back to become an internationally recognised symbol of Australia, the star of books, film and souvenir store shelves.

But numbers are dropping again as human development expands.

'How much can a koala bear?' jokes fireman David Tree, as he offers water to Sam the koala who was made homeless by wildfires in February.

Sam became an international celebrity after her rescue, but she was suffering from a virus called chlamydiosis and later died, during surgery to treat the disease.

Koalas need eucalyptus leaves for both food and water, and therefore must live where there are trees, in the rolling hills or flat, fertile lands that are also preferred by humans for farmland and towns.

"Koalas will actually sleep 18 to 20 hours a day. This is because of their diet. Eucalyptus leaves are high in toxins and very low in energy, so it would be a bit like us eating lettuce all day, every day. We'd be on the lounge (sofa) sleeping a lot."

An unexpected consequence of habitat loss is the onset of a latent disease that infects 50 to 90 percent of the animals, according to studies.

Chlamydiosis is a virus that breaks out in koalas in times of stress, like cold sores in humans, and leads to infections in the eyes and urinary, reproductive and respiratory tracts. It can cause blindness, infertility and death.

"Chlamydia is caused by a couple of different species of Chlamydia, which is different to the one that humans get. Humans get Chlamydia trachomatis and koalas get a different one. And it's spread as a sexually-transmitted disease in koalas mostly, and a little bit through contact. It causes infertility in some animals and also blindness. But in a lot of animals they're able to just carry it fairly normally, without a lot of ill effect."

Experts say the stress of fewer trees for eating and living in has led to outbreaks of the disease.

The problem came to national attention in August, when Sam died.

"Fragmentation and destruction of habitat plays a very big role in causing animals to express diseases more. So, in animals that are living in really good habitat, they're the ones that are able to carry Chlamydia and not necessarily become diseased. But then when they start to have to live in 'third world' conditions, if you like, then they'll become more stressed, and start to express the disease."

The Australian Koala Foundation urged the government to follow up on Sam's case with concrete steps to protect the koala: classifying it a threatened species and implementing policies to stop cutting down habitat.

The organisation named September "Save the Koala" month, with the theme "No Tree, No Me."

The United States already considers the koala a threatened species.

How many koalas remain in the Australian wild is unclear.

The Australian Koala Foundation estimates there are fewer than 100,000 in Australia, down from the millions at the time European settlement started in the late 1700s.

Scientists question that estimate, saying the organisation does not undertake the weeks of bush-walking and tagging required for an accurate count. They think the numbers are slightly higher.

Still, regional counts by scientists and state governments show a huge drop in numbers.

The majority of koalas hug a stretch of eastern coastline in the states of Queensland and New South Wales.

They are most abundant on the so-called Koala Coast, a 155 square-mile (375 square-kilometre) swath of semi-rural coast in south eastern Queensland.

A 2008 survey of the Koala Coast by the Queensland government shows the population dropped 64 percent, from more than 6,200 in 1999 to about 2,800.

While car accidents and dog attacks killed many koalas, the report blamed most of the drop on "excessive habitat loss" and said about 60 percent of the deaths were a result of disease.

Chlamydiosis is not new to koalas. Records from the late 1800s and early 1900s report outbreaks of a disease with the same symptoms within two or three years of a major land-clearing in the area.

"Of those animals that progress to severe disease, it certainly kills quite a lot of them. And probably more importantly for koala populations is that it causes infertility, so animals will live with infertility for quite long periods of time, but they don't produce any young to replace them when they go."

Australia, known for its unique flora and fauna, already counts more than 55 extinct mammals, birds and reptiles.

In 2006, the government's Threatened Species Committee said local population declines did not necessarily mean the koalas were reducing across the whole country and that they were "resilient" enough to live in small or fragmented habitats.

Environment Minister Peter Garrett has ordered a review of the government's conservation strategy.

The two states with the densest koala habitat have taken measures to protect the animal.

New South Wales has classified them as a vulnerable species under the state conservation act, and endangered in two areas. Queensland lists the animal as vulnerable in some parts of the state.