Viral
hepatitis is a serious health problem in the U.S. and throughout the world. While
hepatitis A resolves on its own, hepatitis B and C often result in chronic infection,
which can lead to liver fibrosis, cirrhosis, hepatocellular carcinoma (liver cancer),
and end-stage liver failure. Hepatitis A and B are preventable with a vaccine,
but at this time there is no effective vaccine for hepatitis C.
The healthcare
burden related to chronic hepatitis B and C is expected to escalate in coming
years, as many people infected years or decades ago -- when awareness of the diseases
was poor -- begin to experience the long-term consequences of infection.
However,
the rate of new viral hepatitis infections has fallen dramatically over the past
decade and a half, according to the latest surveillance data from the U.S. Centers
for Disease Control and Prevention (CDC).
The data, published in the March
21, 2008 edition of Morbidity and Mortality Weekly Report Surveillance Summaries,
covers cases of acute viral hepatitis reported in 2006, the most recent year for
which data are available. Such cases are reported voluntarily to the CDC by state
and territory epidemiologists.
Importantly, acute hepatitis B and C often
have no symptoms, so many people do not seek care during this period and thus
would not be reported to the CDC. About 5%-10% of adults infected with hepatitis
B virus - and about 90% of infants -- will go on to develop chronic infection.
With hepatitis C virus, about 75% develop chronic infection.
A summary
of the findings is included below, along with graphs of changes in case rates
for hepatitis A, B, and C, taken from the report. The
full report is available online.
Results
•Hepatitis
A [see Figure
1]:
•
The total number of acute symptomatic hepatitis A cases in 2006 was 3579.
•
After asymptomatic infection and underreporting were taken into account, an estimated
32,000 new infections occurred in 2006.
•
Between 1995 and 2006, hepatitis A incidence declined 90%, to the lowest rate
ever recorded (1.2 cases per 100,000 persons).
•
Declines in hepatitis A were greatest among children and in states where routine
childhood HAV vaccination was recommended beginning in 1999; thus, an increasing
proportion of cases occurred in adults.
• Hepatitis
B [see Figure
9]:
•
The total number of acute symptomatic hepatitis B cases in 2006 was 4713.
•
After asymptomatic infection and underreporting were taken into account, approximately
46,000 new infections occurred.
•
During the 1990-2006 period, acute hepatitis B incidence declined 81%, to the
lowest rate ever recorded (1.6 cases per 100,000 persons).
•
Hepatitis B declines occurred in all age groups, but were greatest among children
under age 15.
•
Hepatitis B declined in all racial/ethnic groups, but was higher for non-Hispanic
blacks (2.3 per 10,000 people).
•
The rate among Asian Americans - a population with a historically high HBV rate
- is now similar to that of Hispanics and non-Hispanic whites (1.1-1.2 case per
100,000 people).
•Hepatitis
C [see
Figure 17]:
•
The total number of
acute symptomatic hepatitis C cases in 2006 was 802, up from 671 in 2005.
•
After asymptomatic infection and underreporting were taken into account, there
were approximately 19,000 new infections in 2006.
•
Following a peak in the late 1980s, the incidence of acute hepatitis C declined
through the 1990s.
•
However, since 2003, hepatitis C rates have plateaued, with a slight increase
in 2006.
•
The 2006 rates were similar across racial/ethnic groups.
•
In 2006, as in previous years, the majority of hepatitis C cases occurred among
adults.
•
Injection-drug use was the most common risk factor.
"The
results documented in this report suggest that implementation of the 1999 recommendations
for routine childhood hepatitis A vaccination in the United States has reduced
rates of infection, and that universal vaccination of children against hepatitis
B has reduced disease incidence substantially among younger age groups,"
the study authors concluded.
They added, however, that, "Higher rates
of hepatitis B continue among adults, particularly males aged 25-44 years, reflecting
the need to vaccinate adults at risk for HBV infection."
"The
decline in hepatitis C incidence that occurred in the 1990s was attributable primarily
to a decrease in incidence among injection-drug users," they wrote. "The
reasons for this decrease were unknown but likely reflected changes in behavior
and practices among injection-drug users." The implementation of needle exchange
programs in many cities likely had a beneficial effect.
The expansion in
2006 of recommendations for routine hepatitis A vaccination to include children
under age 2 is expected to reduce hepatitis A rates still further, the study authors
noted. They added that, "Ongoing hepatitis B vaccination programs ultimately
will eliminate domestic HBV transmission, and increased vaccination of adults
with risk factors will accelerate progress toward elimination.
In the absence
of an effective HCV vaccine, "Prevention of hepatitis C relies on identifying
and counseling uninfected persons at risk for hepatitis C (e.g., injection-drug
users) regarding ways to protect themselves from infection and on identifying
and preventing transmission of HCV in health-care settings."
U.S.
Centers for Disease Control and Prevention, Division of Viral Hepatitis, National
Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention.
4/01/08
Reference A
Wasley, S Grytdal, and K Gallagher. Surveillance for Acute Viral Hepatitis --
United States, 2006. Morbidity and Mortality Weekly Report Surveillanec Summaries
57(SS02): 1-24. March 21, 2008.
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