Retroviruses invading the koala germline contribute to high cancer rates Koalas are facing multiple environmental and health issues which threaten their survival. Along with habitat loss - accelerated by last year’s devastating bush fires – domestic dog attacks and road accidents, they suffer from deadly chlamydial infections and extremely high frequency of cancer. An international team of scientists led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) now demonstrate that a retrovirus invading the koala germline explains the high frequency of koala cancer. The results are reported in the journal Nature Communications. The koala retrovirus (KoRV) is a virus that, like other retroviruses such as HIV, inserts itself into the DNA of an infected cell. At some point in the past 50,000 years, KoRV has infected the egg or sperm cells of koalas, leading to offspring that carry the retrovirus in every cell in their body.