One in every 3,000 blood donors in England could be infected with hepatitis E, new figures suggest.
Experts said that around 1,200 "blood components" containing the virus are likely to be transfused every year in England.
Hepatitis E, caused by the hepatitis E virus, is very rare in the UK and generally results in a mild and short-term infection unless the infected person has a pre-existing liver disease or is pregnant.
While the figure appears to be high, researchers said that the overall burden caused by the infection among people needing blood transfusions is "slight".
The study, published in The Lancet journal and published on World Hepatitis Day, concludes that there appears to be "no pressing need" for blood donors to be screened.
Researchers retrospectively screened 225,000 blood donations collected in the south east of England between October 2012 and September 2013 for the hepatitis E virus (HEV).
They found that 79 donors were infected, a prevalence of about one in every 2,848 donors.
The donations from the infected people were used to prepare 129 blood components - red blood cells, platelets or fresh frozen plasma - and 62 of which were transfused.
Follow-up of 43 "exposed" people who received transfusions showed that transmission had occurred in 42% of patients.
Lead investigator Professor Richard Tedder, from the Blood Borne Virus Unit at Public Health England, said: " HEV genotype 3 infections are widespread in the English population, including blood donors. 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.
"Although rarely causing any acute illness, hepatitis E infections may become persistent in immunosuppressed patients, putting them at risk of future chronic liver disease, and a policy is needed to identify these persistently infected patients and provide them with appropriate antiviral treatment.
"However, our study indicates that the overall burden of harm resulting from transfusion-transmitted HEV is slight.
"Although on a clinical basis alone there appears no pressing need at this time for blood donations to be screened, a broader discussion over harm mitigation is now required."