- Category: HCV Epidemiology & Mortality
- Published on Friday, 14 March 2014 00:00
- Written by Liz Highleyman
An estimated 2.7 million people in the U.S. have chronic hepatitis C, substantially lower than previous estimates, according to an analysis from the National Health and Nutrition Examination Survey(NHANES) published in the March 4 edition of Annals of Internal Medicine. This figure may be an underestimate, however, as the household survey does not include higher-risk populations including homeless and incarcerated people.
Accurate estimates of the number of people living with hepatitis C are particularly important as effective -- and expensive -- new drugs become available and public health officials need to know how many people may require treatment. U.S. guidelines recommend that all Baby Boomers born between 1945 and 1965, as well as anyone with known risk factors, should be screened for hepatitis C virus (HCV) at least once.
Maxine Denniston, Scott Holmberg, and colleagues from the Centers for Disease Control and Prevention (CDC) reported the latest hepatitis C data from NHANES participants surveyed between 2003 and 2010. This periodic national survey looks at a representative sample of U.S. households, and therefore does not include groups such as active duty military, prisoners, homeless people, or people living in institutions or care facilities.
Approximately 5000 survey participants were interviewed in their homes each year about their demographic characteristics and possible exposures and risk factors for HCV infection. Blood samples from participants age 6 or older were tested for HCV antibodies; if positive or indeterminate, samples were tested for HCV RNA, which indicates current chronic infection.
About 25% of people acutely infected with HCV naturally clear the virus, while the rest develop chronic infection lasting more than 6 months. Effective antiviral therapy can make HCV RNA viral load undetectable, but antibodies remain in people with either spontaneous or treatment-induced viral clearance.
- 386 participants tested positive for HCV antibodies and 273 tested positive for HCV RNA, out of the total 30,074 who completed interviews and gave blood samples.
- The estimated prevalence of HCV antibodies was 1.3%, and the estimated prevalence of chronic infection was 1.0%.
- The best estimate for the total number of people with HCV antibodies in the non-institutionalized civilian population was 3.6 million (with a confidence interval of 3.0 to 4.2 million), while the estimate for chronic hepatitis C was 2.7 million (with a confidence interval of 2.2 to 3.2 million).
- Most people with chronic hepatitis C (81%) were born between 1945 and 1965; this age group had an estimated prevalence of 2.6%.
- Only 2 people aged 6 to 19 had evidence of chronic HCV infection.
- Men were more likely to have hepatitis C than women, making up nearly two-thirds of chronic infections.
- Other demographic factors associated with HCV infection included black race/ethnicity, being born in the U.S., lower education level (high school or less), and lower family income (less than twice the federal poverty level).
- Only 3 people with chronic HCV infection tested positive HIV coinfection (although participants were permitted to opt out of HIV testing).
- Significant behavioral risk factors among people age 20-59 were "illicit" drug use (including injection drugs, but not marijuana), having 10 or more lifetime sexual partners, and receiving a blood transfusion before 1992 (NHANES does not ask people over age 60 about drug use or sexual behavior).
- Half of all people with chronic HCV, however, did not report a history of either drug injection or blood transfusions.
"This analysis estimated that approximately 2.7 million U.S. residents in the population sampled by NHANES have chronic HCV infection, about 500,000 fewer than estimated in a similar analysis between 1999 and 2002," the researchers concluded. "These data underscore the urgency of identifying the millions of persons who remain infected and linking them to appropriate care and treatment."
The most commonly cited estimate of the number of people with chronic hepatitis C has been 3.9 million, based on earlier NHANES data. But that estimate may have been low, given higher HCV infection rates among excluded groups including homeless and incarcerated people.
A recent study by researchers from Emory University found that among 12 states that performed routine testing between 2001 and 2012, hepatitis C antibody seroprevalence among prison inmates ranged from 10% to 41%. All but 1 state had declining prevalence. The researchers estimated the national prisoner seroprevalence rate to be 17% in 2006, and based on the estimated size of total U.S. correctional population, they estimated that 1,857,629 HCV antibody positive people were incarcerated that year. They further estimated that incarcerated people represented 29% to 33% of the total number of U.S. hepatitis C cases in 2006, down from 39% in 2003.
"Our results provide an important updated estimate of hepatitis C seroprevalence and suggest that correctional populations bear a declining but still sizable share of the epidemic," the Emory team wrote.
The current analysis may suggest a decrease in HCV antibody prevalence from 1.8% during 1988-1994 and 1.6% during 1999-2002, or a possible decrease in chronic HCV infections from 1.3% during 1999-2002, the CDC authors noted. But the confidence intervals -- or range within which the true number is likely to fall -- overlap, so the difference may reflect statistical variability.
"An important public health implication is that our analysis suggests decreases in prevalence that probably reflect increasing mortality from HCV-related conditions," they explained. Another recent study found that deaths related to hepatitis C are likely undercounted.
"Although increased successful treatment of HCV infection might also cause a decrease in prevalence estimates since the last survey, all available current information indicates that no more than one half of persons with chronic HCV infection have been tested for anti-HCV [antibodies]; many who are anti-HCV-positive do not receive medical care or confirmatory HCV RNA testing; and, if positive, few to date have received antiviral therapy and achieved sustained virologic response indicative of cure," Denniston and colleagues wrote. "Thus, differences in prevalence due to successful treatment are unlikely."
"The availability of new, direct-acting antiviral medications with higher success rates creates an enormous opportunity to prevent morbidity and mortality among persons with chronic HCV infection," the authors continued. "However, the health impact of advances in HCV therapy can be realized only when HCV-infected persons are tested, identified, and linked to appropriate care and treatment."
MM Denniston, RB Jiles, J Drobeniuc, S Holmberg, et al. Chronic Hepatitis C Virus Infection in the United States, National Health and Nutrition Examination Survey 2003 to 2010. Annals of Internal Medicine 160(5):293-300. March 4, 2014.
AK Varan, DW Mercer, MS Stein, and AC Spaulding. Hepatitis C Seroprevalence Among Prison Inmates Since 2001: Still High but Declining.Public Health Reports. March-April 2014.