Hepatitis E virus, known to cause liver disease, is found among one in almost 3,000 blood donors in England, said a study Monday that sparked a call for screening in Europe.
Published on World Hepatitis Day, a study in The Lancet medical journal said a systematic analysis of donated blood showed that 79 out of 225,000 donations were infected with a version of the virus, genotype 3, most prevalent in developed countries.
Humans can contract it from infected pigs and contaminated blood or drinking water.
Transmission of the virus had occurred in 18 of 43 exposed blood recipients, the authors said.
One developed mild clinical hepatitis.
"HEV genotype 3 infections are widespread in the English population, including blood donors," said principal investigator Richard Tedder from the Blood Borne Virus Unit at Public Health England.
"We estimate that between 80,000 and 100,000 human HEV infections are likely to have occurred in England during the year of our study."
Similar prevalences had previously been reported in Sweden in Germany, suggesting the virus was widespread on the European continent, said the study.
Most people who contract the virus recover from symptoms including appetite loss and fever without treatment, but it can be dangerous for those with a suppressed immune systems, like cancer patients and organ transplant recipients, as well as pregnant women.
There is no cure.
The study authors said the overall risk was slight, and "there appears to be no pressing need at this time for blood donations to be screened."
In a comment carried by The Lancet, however, Jean-Michel Pawlotsky from the Henri Mondor hospital in Paris, said this conclusion was "surprising".
On his own reading of the results, "systematic screening of blood components for markers of hepatitis E infection should be implemented in areas where HEV is endemic" -- including the European Union.
Two other papers carried by the journal reported successes in trials with two pill-form antiviral drugs in treating hepatitis C, a blood-borne liver disease that affects about 150 million people worldwide and is often transmitted through needle-sharing.
It is a major cause of liver failure and cancer.
The two drug regimens hold promise for a safer, shorter and simpler cure, said the papers -- one took only 12 weeks to work compared to older injection-pill combination treatments that could last up to a year.
"In the future, very-short-duration, all-oral (antivirals) should improve treatment uptake and success," Ed Gane, director of the New Zealand Liver Transplant Unit at Auckland City Hospital wrote in a comment.
The only barrier to achieving this goal would be the cost of treatment, he added.