Testing for hepatitis C, a major cause of liver cancer, is lagging behind among the group of Americans with the highest rate of infection: baby boomers.

A study published Tuesday showed that only about 13 percent of baby boomers were tested in 2015, up just slightly from 12 percent in 2013. US public health authorities recommend all people in that demographic — those born between 1945 and 1965— be screened for hepatitis C.

‘‘If we want to make a dent in the rising rate of liver cancer, we need to get the population with a high rate of infection screened and treated,’’ said Susan Vadaparampil, the study’s senior author and a researcher at Moffitt Cancer Center in Tampa.

While mortality rates for many cancers are decreasing, deaths from liver cancer rose 56 percent from 2003 to 2012. The strongest single predictor of the disease is chronic hepatitis C infection. Almost 80 percent of the people in the United States who have hepatitis C infections are baby boomers.

Most contracted the virus long before it was discovered in 1989. Many do not have any symptoms and do not realize they are infected. Vadaparampil said researchers are not sure why the infection rate in this group is so high but suspect it may be linked to past use of illicit injected drugs or other risky behaviors.

WASHINGTON POST