Koalas are unique to Australia and have become symbols of the country, but their numbers are in sharp decline and the species' survival may be in peril.
One of the most common places to find a koala these days is in the hospital, and one of the reasons is the sexually transmitted disease chlamydia.
In people, chlamydia is a common sexually transmitted disease. A different strain infects koalas, but it too can be spread sexually, and it's causing an epidemic.
In some parts of Australia, koala infection rates are as high as 90 percent.
Chlamydia affects male and female koalas, and even the little ones called joeys - who pick it up early when suckling from their mothers in the pouch.
It causes blindness and infertility in koalas - and can be fatal.
Visible signs of infection include conjunctivitis, and a condition dubbed "dirty tail," caused by a combination of urinary tract infections and incontinence.
Some other animals are also infected with the disease but it is usually at low levels. It affects koalas more seriously and experts don't know why that is.
But, as in humans, the disease is treatable with antibiotics.
This means keeping the animals in captivity for the duration of the koala chlamydia treatment - usually a few months - before releasing it back into the wild.
Elaborate efforts are already underway. Hopefully they succeed.