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U.S. Hepatitis C Incidence Dropped 10-fold Over 2 Decades

SUMMARY: The incidence of acute hepatitis C virus (HCV) infection in the U.S. has decreased dramatically over the past 25 years, falling from 7 to 0.7 cases per 100,000 people, according to a CDC study published in the February 14, 2011, Archives of Internal Medicine. In recent years nearly half of all new infections were attributable to injection drug use, but about a third had no identifiable risk factor.

By Liz Highleyman

Formerly known as "non-A/non-B" hepatitis, HCV was identified in the late 1980s. HCV is transmitted through direct blood contact. Donated blood in the U.S. has been screened for HCV since 1992. The most common route of transmission today is blood left on shared needles and other drug-injection equipment.

Ian Williams and colleagues with the Centers for Disease Control and Prevention (CDC) used sentinel surveillance methods to determine incidence (new infections) and transmission patterns of acute hepatitis C in the U.S., looking at data from 25 years of general population surveillance.

The researchers identified cases of acute HCV infection between 1982 and 2006 using a stimulated passive surveillance system in 4-6 U.S. counties. Cases were determined based on sudden onset of symptoms and/or elevated alanine aminotransferase (ALT) liver enzyme levels (> 2.5 times the upper limit of normal [xULN]), positive HCV antibody or RNA tests, but negative hepatitis A and B tests.

Clinical cases generally reflect only about 20% to 30% of all newly acquired infections, they noted, since acute hepatitis C is often asymptomatic.


A total of 2075 individuals with acute HCV infection were identified, with a median age of 31 years:
91.5% had ALT values greater than 7 x ULN;
77.3% developed jaundice, or yellowing of the skin and eyes;
22.5% were hospitalized;
1.2% died.
The average HCV incidence was 7.4 per 100,000 people (or about 70 per 1 million) during 1982-1989, falling to 0.7 per 100,000 (or 7 per 1 million) during 1994-2006.
Among 1748 patients interviewed, injection drug use was the most commonly reported risk factor.
The average number of injection drug-related acute infections declined in parallel with the overall decrease.
However, the proportion of injection drug-related cases rose from 31.8% during 1982-1989 to 45.6% during 1994-2006.
Almost all individuals (91.8%) with injection drug-related acute hepatitis C during 1994-2006 had been in a drug treatment program and/or incarcerated.
The number of new HCV infections transmitted through blood transfusions declined dramatically after the blood screening test became available, and during 1994-2006 only 5 possible cases were identified.
About one-third of acute HCV cases had no identifiable risk factor.

Based on these findings, the study authors concluded, "The incidence of acute HCV declined substantially over the 25 years of population-based surveillance."

"Despite declines," they added, "injection drug use is the most common risk factor for new HCV infection."

Investigator affiliations: Division of Viral Hepatitis, Centers for Disease Control and Prevention (CDC), Atlanta, GA; Outbreak Response and Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, CDC, Atlanta, GA; National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, GA; Office of the Director, National Center for Immunization and Respiratory Diseases, CDC, Atlanta, GA; Division of Infectious Diseases, University of Texas Medical Branch, Galveston, TX.


IT Williams, BP Bell, W Kuhnert, and others. Incidence and transmission patterns of acute hepatitis C in the United States, 1982-2006. Archives of Internal Medicine 171(3): 242-248 (abstract). February 14, 2011.























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