Epidemiology of HCV and Norovirus: August 2006
Armstrong GL, Wasley A, Simard EP, McQuillan GM, Kuhnert WL, Alter MJ. The prevalence of hepatitis C virus infection in the United States, 1999 through 2002. Ann Intern Med. 2006;144:705-714. An attempt was made to determine the hepatitis C virus (HCV)-infected population in the United States with data from the Third National Health and Nutrition Examination Survey (NHANES III), which was conducted in 1988-1994. That study showed that about 1.8% of the US population had anti-HCV antibody, indicating that a total of 3.9 million persons had prior HCV infection and approximately 2.7 million had chronic infection. Most of the seropositive persons were between 30 and 49 years of age and had been infected for less than 20 years. The pattern of age-specific prevalence suggested that the incidence of infection increased substantially in the 1960s and 1970s, and peaked in the 1980s. The present study used survey data from 1999 to 2002 to determine the more contemporary prevalence of HCV infection.
Methods: The study was again done with survey results from NHANES III, which is a nationally representative household survey of the US civilian, noninstitutionalized population. The survey included 15,079 persons who provided a blood sample and were over 6 years of age. These participants were interviewed for relevant information and blood was tested for HCV antibody; those who were positive were also tested for HCV RNA.
Results: Results were based on an analysis of 15,079 participants. The overall prevalence of anti-HCV was 1.6%; this extrapolates to an estimated 4 million persons who are seropositive for HCV, and the HCV RNA data suggested that the total number with chronic HCV infection is approximately 3.2 million. The peak age of high prevalence was 40-49 years, 10 years greater than with the 1988-1994 survey. The comparative data for these 2 sequential analyses that were separated by approximately 10 years are shown in Table 1 .
Table 2 shows the anti-HCV distribution by sex, income, receipt of blood transfusions before 1992, injection drug use history, herpes simplex virus (HSV) as a surrogate for sexually transmitted disease, age associations, and alanine aminotransferase (ALT) levels as an indication of liver disease. Table 2 also shows the prevalence of HCV and the total number of cases expected in that defined population when extrapolated to the total US population.
Conclusion: The study authors conclude that the prevalence of HCV is relatively high and stable at about 1.6% to 1.8%. The great majority of these patients were 20-59 years of age. Of these, 48% reported a history of injection drug use, which was clearly the strongest risk factor; other important risk factors were over 20 lifetime sex partners or blood transfusions before 1992. Thus, despite a decrease in new HCV infections, the prevalence in a population-based study has remained relatively stable due primarily to aging of persons who acquired this infection many years ago.
Comment: In the accompanying editorial, Jules Dienstag notes that, despite a dramatic 80% decrease in the annual incidence of acute HCV infection in the 1990s, the recent survey summarized above showed that the prevalence of HCV has remained relatively constant; the most remarkable change is a 10-year increase in the age of those infected. Injection drug use accounted for approximately half of the patients in the category 20-59 years of age, and much of this infection was apparently remote rather than recent. This risk was about 150-fold higher than for persons who did not report use of injected drugs. Of interest, there are data supporting the role of sexual transmission of HCV, although rates are a small fraction of the risk associated with injecting drug use.
Hepatitis C Virus
Armstrong GL, Wasley A, Simard EP, McQuillan GM, Kuhnert WL, Alter MJ. The prevalence of hepatitis C virus infection in the United States, 1999 through 2002. Ann Intern Med. 2006;144:705-714. An attempt was made to determine the hepatitis C virus (HCV)-infected population in the United States with data from the Third National Health and Nutrition Examination Survey (NHANES III), which was conducted in 1988-1994. That study showed that about 1.8% of the US population had anti-HCV antibody, indicating that a total of 3.9 million persons had prior HCV infection and approximately 2.7 million had chronic infection. Most of the seropositive persons were between 30 and 49 years of age and had been infected for less than 20 years. The pattern of age-specific prevalence suggested that the incidence of infection increased substantially in the 1960s and 1970s, and peaked in the 1980s. The present study used survey data from 1999 to 2002 to determine the more contemporary prevalence of HCV infection.
Methods: The study was again done with survey results from NHANES III, which is a nationally representative household survey of the US civilian, noninstitutionalized population. The survey included 15,079 persons who provided a blood sample and were over 6 years of age. These participants were interviewed for relevant information and blood was tested for HCV antibody; those who were positive were also tested for HCV RNA.
Results: Results were based on an analysis of 15,079 participants. The overall prevalence of anti-HCV was 1.6%; this extrapolates to an estimated 4 million persons who are seropositive for HCV, and the HCV RNA data suggested that the total number with chronic HCV infection is approximately 3.2 million. The peak age of high prevalence was 40-49 years, 10 years greater than with the 1988-1994 survey. The comparative data for these 2 sequential analyses that were separated by approximately 10 years are shown in Table 1 .
Table 2 shows the anti-HCV distribution by sex, income, receipt of blood transfusions before 1992, injection drug use history, herpes simplex virus (HSV) as a surrogate for sexually transmitted disease, age associations, and alanine aminotransferase (ALT) levels as an indication of liver disease. Table 2 also shows the prevalence of HCV and the total number of cases expected in that defined population when extrapolated to the total US population.
Conclusion: The study authors conclude that the prevalence of HCV is relatively high and stable at about 1.6% to 1.8%. The great majority of these patients were 20-59 years of age. Of these, 48% reported a history of injection drug use, which was clearly the strongest risk factor; other important risk factors were over 20 lifetime sex partners or blood transfusions before 1992. Thus, despite a decrease in new HCV infections, the prevalence in a population-based study has remained relatively stable due primarily to aging of persons who acquired this infection many years ago.
Comment: In the accompanying editorial, Jules Dienstag notes that, despite a dramatic 80% decrease in the annual incidence of acute HCV infection in the 1990s, the recent survey summarized above showed that the prevalence of HCV has remained relatively constant; the most remarkable change is a 10-year increase in the age of those infected. Injection drug use accounted for approximately half of the patients in the category 20-59 years of age, and much of this infection was apparently remote rather than recent. This risk was about 150-fold higher than for persons who did not report use of injected drugs. Of interest, there are data supporting the role of sexual transmission of HCV, although rates are a small fraction of the risk associated with injecting drug use.
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