acute HBV infection, suggesting that the actual
number of new cases in the United States (including
asymptomatic patients and those who seek no care)
was actually closer to 19,000, as each reported case
of HBV is estimated to represent roughly 6.5 actual
infections6 Acute infection is symptomatic in up to
50% of adult cases; infants and children are usually
asymptomatic.4 Acute HBV infection most often resolves
completely and confers lifelong immunity, but in
up to 2% of cases, infection results in fulminant hepatitis,
which has a case fatality rate of 63% to 93%.
Acute HBV progresses to chronic infection in
about 90% of infants infected at birth, 30% to 50%
of children ages one to five, and 5% of adults. People
with a compromised immune system are at elevated
risk of developing chronic infection. Those
with chronic infection tend to be asymptomatic carriers,
though roughly 25% eventually develop cirrhosis
or hepatocellular carcinoma. An estimated
240 million people worldwide and 700,000 to 1.4
million people in the United States are chronically
infected with HBV.