Doctors fear that the virus, provisionally called Hepatitis G or GBV- C, could cause serious liver disease including cirrhosis and cancer, and could be even more widespread than Hepatitis B, which affects 350 million people worldwide.
They want more resources to be channelled into developing an effective screening test.
The discovery of the new virus comes less than a decade after the Hepatitis C virus was isolated, and only five years since a test for that virus was introduced into the blood transfusion service. It is now thought that about 300,000 people in the UK are infected with Hepatitis C, of whom 70,000 could develop cirrhosis or cancer of the liver. More than 5,000 contracted the disease through blood transfusions.
"The isolation of this new virus is a very important scientific discovery," said Dr Geoffrey Dusheiko, reader in medicine at the Royal Free Hospital School of Medicine in London. "There is an urgent need to develop a simple antibody test.
"About 1.5 per cent of blood donors have been found to be positive for the virus, using what is known as a polymerase chain reaction (PCR) test. This test is not suitable for screening large numbers of donors.
"We need to study Hepatitis G positive blood donors, to discover whether they have underlying silent liver disease. All this needs to be begun as soon as possible."
Dr Lesley Kay, consultant haematologist and medical director of Medical Diagnostic Laboratories Ltd, said that this latest discovery was "the story of the blood transfusion service over the last 15 years. We are always chasing the next virus.
"New viruses will continue to appear while we have exotic holidays, foreign travel and sexual freedom. These viruses often exist in small human or animal populations for many years without spreading. Visitors travel to the region, contract the virus and take it back home. It enters the blood supply and is spread by that route or by sexual transmission."
Two groups of scientists in the United States appear to have independently identified the new virus.
Professor Arie Zuckerman, of the World Health Organisation Collaborating Centre for Reference and Research on Viral Diseases at the Royal Free Hospital, said: "We don't have a lot of data about it. It has been found in some patients with acute or chronic hepatitis, fulminant hepatitis in Japan, intravenous drugs users, haemophiliacs, frequently transfused patients and blood donors.
"Much more work needs to be done on the virus, but there is inadequate support for hepatitis research in Britain."
The Department of Health admitted yesterday that a test was needed but said it was not carrying out any work to find one. A spokesman said: "The Committee on the Microbiological Safety of Blood and Tissue for Transplant was appraised of the available information on Hepatitis G in January.
"We are at an early stage of clinical knowledge," he added.
A Medical Research Council spokesman said: "Applications for research work on hepatitis are treated like any other application. But there is not enough money to go round."Reuse content