CDC Reports Dramatic Declines in New Cases of Hepatitis A, B, and C

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

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."

03/23/07

Reference

A Wasley, J T Miller, and L Finelli. Surveillance for Acute Viral Hepatitis -- United States, 2005. Morbidity and Mortality Weekly Report: Surveillance Summaries. 56 (SS-3). March 16, 2007.