For some people, hepatitis B is a short illness, but for others, it can become long term or chronic and lead to serious liver problems, including cirrhosis and liver cancer. Now, new research finds that the risk of liver cancer persists even after the virus is cleared, suggesting that people who have had the illness should continue to be monitored.

For their study, the researchers selected participants from a group of 1,346 Alaska-Native patients with chronic HBV infection who were followed during 1982-2013. They selected 238 patients whose chronic HBV infection resolved during the follow-up and matched them to 435 patients who remained infected (the controls). The patients were matched by age, gender and HBV strain. The team found that clearance of HBV appeared to make no difference to the risk of developing liver cancer. The researchers note while we do not know why HBV clearance appears not to affect risk of liver cancer; they suggest it is likely due to a number of factors. One reason, for instance, could be the integration of HBV DNA into the genome of liver cells, which occurs early in infection, and can persist after traces of the virus clear from the bloodstream. The authors note that a “substantial proportion” of the case patients in their study had a detectable level of HBV DNA after virus traces (antibodies against the virus) had cleared from the bloodstream. This raises the possibility that “ongoing low-level HBV DNA replication with continued integration” into the host liver cell contributes to the persistent risk of liver cancer after the virus has cleared from the bloodstream.