Hepatitis B virus infection may either be acute (self-limiting) or chronic (long-standing). Persons with self-limiting infection clear the infection spontaneously within weeks to months.
Children are less likely than adults to clear the infection. More than 95% of people who become infected as adults or older children will stage a full recovery and develop protective immunity to the virus. However, this drops to 30% for younger children, and only 5% of newborns that acquire the infection from their mother at birth will clear the infection. This population has a 40% lifetime risk of death from cirrhosis or hepatocellular carcinoma. Of those infected between the age of one to six, 70% will clear the infection.
Hepatitis D (HDV) can only occur with a concomitant hepatitis B infection, because HDV uses the HBV surface antigen to form a capsid. Co-infection with hepatitis D increases the risk of liver cirrhosis and liver cancer. Polyarteritis nodosa is more common in people with hepatitis B infection.
Reactivation
Hepatitis B virus DNA persists in the body after infection and in some people the disease recurs. Although rare, reactivation is seen most often in people with impaired immunity.] HBV goes through cycles of replication and non-replication. Approximately 50% of patients experience acute reactivation. Male patients with baseline ALT of 200 UL/L are three times more likely to develop a reactivation than patients with lower levels. Patients who undergo chemotherapy are at risk for HBV reactivation. The current view is that immunosuppressive drugs favor increased HBV replication while inhibiting cytotoxic T cell function in the liver.