He said Chlamydia pneumoniae was originally an animal pathogen that crossed the species barrier to humans and had adapted to the point where it could now be transmitted between humans.

"What we think now is that Chlamydia pneumoniae originated from amphibians such as frogs," he said.

Professor Timms said it was important to understand the origins of zoonotic infections to know the risk animal infections have to humans.

"It means we can look for solutions such as developing improved diagnostic tests, ensuring people take appropriate precautions to prevent the disease spreading and also develop vaccines," he said.

Assistant Professor Garry Myers from the Institute for Genome Sciences said the findings indicated that the high disease burden of Chlamydia pneumoniae in humans may represent a major public health corollary of zoonotic infections.

Source: Queensland University of Technology