This is second major ethnic group -- the other being blacks -- found not to respond well to the therapy, consisting of pegylated interferon with ribavirin, in recent years.

"Hispanics and African-Americans have a higher prevalence of hepatitis C than other groups, so it is imperative that we figure out what is behind the poor response rate, and continue to do clinical trials on new forms of therapies," study second author Dr. Lennox Jeffers, a professor of medicine at the University of Miami Miller School of Medicine, said in a news release issued by the university.

Jeffers served as principal investigator of the 2006 study that found blacks responded poorly to treatment for hepatitis C.

The new study, published in the Jan. 15 issue of The New England Journal of Medicine, looked at 269 Hispanic and 300 non-Hispanic white hepatitis C patients from across the country.

"This clearly tells us there may be factors that impact liver disease in Hispanics that we do not yet understand," senior author Dr. Paul Martin, chief of hepatology at the Miller School, said in the news release.

The researchers noted that the Hispanic population has been underrepresented in past hepatitis C studies, and more research into how the disease affects this ethnic group is necessary.

The hepatitis C virus, which is contracted through exposure to blood already tainted with the virus, can lead to liver cancer, liver failure or cirrhosis. Liver transplant can sometimes be the only option for survival.

Protease inhibitors, which are used in combination therapy to treat HIV, are being explored by some researchers as an additional treatment for hepatitis C.

More information

The U.S. Centers for Disease Control and Prevention has more about hepatitis C.