Hepatitis
B and C have become growing public health concerns in recent years, as people
infected decades ago begin to develop complications of chronic liver disease,
including cirrhosis and hepatocellular
carcinoma.
But
the rates of new hepatitis A, B, and C infections have decreased dramatically
over the past 10-15 years, according to a new surveillance study by the Centers
for Disease Control and Prevention (CDC), published in the March 16, 2007 issue
of Morbidity and Mortality Weekly Report.
Hepatitis
A virus (HAV) is spread via the fecal-oral route, primarily through contaminated
food and water. Hepatitis B virus (HBV) and hepatitis C virus (HCV) are transmitted
via blood-to-blood contact, for example sharing needles to inject drugs; they
can also be transmitted through sexual contact and from mothers to babies during
pregnancy or delivery.
Findings
•
Overall, approximately 100,000 Americans were newly infected with viral hepatitis
in 2005, compared with about 500,000 in 1995.
•
In 2005, a total of
4488 cases of acute symptomatic hepatitis A were reported, for an incidence rate
of 1.5 per 100,000 persons.
•
After asymptomatic
infections and underreporting were taken into account, the estimate was 42,000
new infections.
•
Since 1995, reported
cases of acute hepatitis A decreased by 88%.
•
In 2005, a total of
5494 cases of acute symptomatic hepatitis B were reported, for an incidence rate
of 1.8 per 100,000 persons.
•
After accounting for
asymptomatic infections and underreporting, the estimated total was 51,000 new
infections.
•
Since 1990, reported
new cases of hepatitis B declined by 79%.
•
In 2005, a total of
671 cases of confirmed acute hepatitis C were reported, for an incidence rate
of 0.2 per 100,000 persons.
•
After accounting for
asymptomatic infections and underreporting, the estimated total was 20,000 new
infections.
•
Since 1992, new cases
of hepatitis C declined by 92% among persons aged 25-39 years.
Discussion
The
rates of new hepatitis A and B cases reported in 2005 were the lowest ever recorded.
"The sharp declines in rates of hepatitis A and B are one of the
big public health success stories of the last 10 years," said Kevin Fenton,
director of the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD and TB
Prevention.
The
decrease in hepatitis A and B is not surprising, due to the availability of effective
vaccines. The HBV vaccine became available in 1981 and the HAV vaccine in 1995.
Both are now included in the recommended vaccination series for all infants.
"Rates
are declining for all ages, but much of the decline is driven by declining rates
in children, which is the age group that has been covered by routine vaccination
for both hepatitis A and B," said lead author Annemarie Wasley of the CDC.
Although
there is no vaccine for HCV -- which was only identified in 1989 -- infection
rates have also fallen. This is partly attributable to screening of donated blood
and decreased infections among healthcare workers due to better awareness and
adoption of universal precautions to prevent HIV infection. But rates have fallen
most dramatically among injection drug users (IDUs), as education and needle exchange
programs have reduced the sharing of injection equipment.
Viral hepatitis
surveillance data are limited by the fact that many acute infections with all
3 viruses are asymptomatic, and therefore never reported. Hepatitis A resolves
without treatment. Hepatitis B becomes chronic in about 10% of infected adults
(and 90% of infected infants), while hepatitis C becomes chronic in about 75%
of cases. Hepatitis B and C can cause severe liver disease, but this usually takes
many years to develop (although progression appears to be more rapid in HIV positive
people).
"Although the declines in acute viral hepatitis are promising,
the number of new infections remains high particularly among unvaccinated adults,"
said John Ward, director of CDC's Division of Viral Hepatitis. "We need to
encourage vaccination of adults at high risk for hepatitis B, particularly those
with multiple sex partners or whose sex partners are already infected, men who
have sex with men, and injection drug users."
"Ongoing hepatitis
B vaccination programs will ultimately eliminate domestic HBV transmission, and
increased vaccination of adults who have risk factors will accelerate progress
toward elimination," the researchers concluded. "Prevention of hepatitis
C relies on identifying and counseling uninfected persons at risk for hepatitis
C (e.g., IDUs) regarding ways to protect themselves from infection."
