A virus that causes a rare type of leukemia has found in the genome of bats. The traces of ancient DNA have filled that last major gap in the fossil record of retrovirus; the Deltaretrovirus.

The Deltaretrovirus group were suspected of infecting human during the pre-historic times. But researchers cannot provide evidence because these viruses do not leave any fossil records to trace and study their deeper origin.

With the discovery of the Deltaretrovirus, it will fill the viral sequence of the last major gap of fossils among retroviruses. It also provides a measurement to calculate the timeline of interaction between the hosts and deltaretroviruses, according to Dr. Robert Gifford from the University of Glasgow Centre for Virus Research.

T-lymphotropic viruses belong to the group of Deltaretrovirus, it causes a rare type of Non-Hodgkin Lymphoma known as Adult T-Cell Leukemia/Lymphoma (ATLL). It infects 15 to 20 million people worldwide, and those who carry this kind of virus do not often develop any signs and symptoms.

The remnants of deltaretrovirus found in the genome of bent-winged bats. The sequence found was distantly related to Minopterid species which originated over 20 to 45 million years ago.

The team worked with Dr. Gifford found unusual and unexplained features of the virus present in contemporary deltaretroviruses. This characteristic discovery indicates that deltaretroviruses were defined million years ago.

In addition, this can be a tool to understand the mechanism of mammals in the defense against the threat from these viruses. It is important for researchers to understand the details of the history of deltaretroviruses to find out how they affect humans and animals now and in the future.