| New Findings Suggest
Higher U.S. Hepatitis C Rate By
Liz Highleyman
The most common estimate for the number of hepatitis C cases in the United States
is 3.9 million, based on data from the previous National Health and Nutrition
Examination Survey (NHANES), a representative household survey conducted between
1988 and 1994. Now, new data from the most recent NHANES, conducted between 1999
and 2002, suggest that 4.1 million may be a more accurate estimate. The
earlier NHANES estimated that 1.8% of U.S. residents - 3.9 million - had been
infected with hepatitis C virus (HCV), and that 70% of these (2.7 million) had
chronic hepatitis C. A majority (65%) of HCV-positive individuals were in the
30-49 age bracket. The
latest survey, which included more than 15,000 people aged 20-59 years who were
interviewed about their health status and provided blood samples for evaluation,
indicated that the hepatitis C prevalence rate has declined slightly, to 1.6%.
However, given an increase in the total population, the new estimate of the number
of people with hepatitis C is higher, at 4.1 million, with 3.2 million of these
having chronic infection. The
new data showed that a majority of hepatitis C cases are now found within an older
group, aged 40-49, illustrating the aging of a cohort that was infected in the
past (often due to occasional injection drug use in the 1960s-1980s). Among this
age group, the estimated HCV prevalence was 4.3%. Since the identification of
HCV in 1989 and the development of blood screening test in 1992, the rate of new
infections has fallen dramatically, so the prevalence is lower in younger age
groups. Nearly
half (48.4%) of HCV-infected adults aged 20-59 years reported a history of injection
drug use (most at least one year in the past, and often decades ago). In an editorial
accompanying the NHANES report, Jules Dienstag, MD, said that “a self-limited
epidemic of injection drug use over several decades” has led to a “delayed,
bitter harvest of chronic liver disease.” Other
factors associated with HCV infection in the latest NHANES included non-injection
drug use, more than 20 lifetime sexual partners, male sex, lower income, and lower
education level. Within the 40-49 age group, non-Hispanic blacks had an estimated
HCV prevalence of 9.4%, compared with 3.8% among non-Hispanic whites. While
the new estimate likely better reflects reality, it still may be too low. NHANES,
which focuses on households, excludes certain groups at higher risk for HCV infection
than the population as a whole. At
the American Association for the Study of Liver Diseases (AASLD) conference in
November 2005, Brian Edlin, MD, presented an estimate of the number of people
and the HCV prevalence rates in these excluded groups, including incarcerated
individuals (nearly two million, with an estimated HCV prevalence rate of 32%),
homeless people (more than 800,000; 35%), hospitalized patients (approximately
650,00; 17%), nursing home residents (more than 1,600,000; 5%), and active-duty
military personnel (approximately 1,400,000; 0.5%). Taking these groups into account,
Edlin suggested that a more accurate estimate of the total number of U.S. hepatitis
C cases may be 5 million, including 3.4 million with chronic infection. The
authors of the latest NHANES concluded that most HCV-positive adults (about 85%)
could be identified by targeted testing of individuals aged 20-59 with elevated
alanine aminotransferase (ALT) levels, those with a history of injection drug
use, and those who received blood transfusions prior to 1992. Identification
of HCV-positive individuals is increasingly important as these patients reach
the age and duration of infection at which long-term HCV-related liver complications
- including cirrhosis and hepatocellular carcinoma - begin to develop. Survey
data showed that many HCV-infected individuals continued to drink alcohol and
had not received the recommended hepatitis A and B vaccines. 6/6/06 Reference G.
Armstrong, A. Wasley, E.P. Simard, and others. The prevalence of hepatitis C virus
infection in the United States, 1999 through 2002. Annals of Internal Medicine
44(10): 705-714. May 16, 2006. A.
Dienstag. Hepatitis C: a bitter harvest. Annals of Internal Medicine
44(10): 770-771. May 16, 2006. B.
Edlin. Five million Americans infected with the hepatitis C virus: a corrected
estimate. Abstract 44. 56th American Association for the Study of Liver Disease
meeting. November 11-15, 2005. San Francisco, CA.
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