In some welcome news, Welsh scientists say their successful cloning of a human virus could lead to new treatments for life-threatening diseases.
Human cytomegalovirus (HCMV) is a major infectious cause of congenital malformations worldwide. The virus is also known to cause life-threatening disease in transplant patients and people with HIV/AIDS.
The development of new treatments has been hampered, as scientists have been unable to stably replicate HCMV outside the human body.
Dr Richard Stanton from Cardiff University's School of Medicine who led the joint research, said: "HCMV has by far the largest genome of all viruses affecting humans - consequently it was technically difficult to clone in an intact form in the laboratory.
"Cloning a copy of the virus from a strain isolated by Cardiff Public Health Laboratories has enabled us to identify the genes causing the instability of the virus outside the body.
"Following the identification of these genes, we have successfully developed cells in which we can grow virus that corresponds to that which exists in the human body."
Cloning the virus for the first time will help virologists develop antivirals and vaccines against the virus that causes clinical disease.
The virus, named Merlin, was isolated from a clinical sample identified by the Diagnostic Unit, Public Health Wales.
The study has been published in the Journal of Clinical Investigation.