Elsevier

Annals of Epidemiology

Volume 16, Issue 11, November 2006, Pages 812-819
Annals of Epidemiology

Estimated Incidence of Hepatitis A Virus Infection in Catalonia

https://doi.org/10.1016/j.annepidem.2006.02.005Get rights and content

Purpose

Hepatitis A normally is underreported by statutory disease reporting systems. The objective of this study is to estimate the incidence of hepatitis A virus (HAV) infection from prevalence surveys of infection carried out in representative samples of the population in 1989, 1996, and 2002 and the reported disease incidence during 1991 to 2003 in Catalonia.

Methods

The real incidence of the infection was estimated from the reported incidence adjusted by the prevalence of susceptible individuals and the probability of presenting clinical manifestations. The bootstrap resampling technique was used to calculate 95% confidence intervals (CIs) of reported, clinical, and all infection cases.

Results

The infection rate estimated by the bootstrap method was 31.1/100,000 person-years (bootstrap studentized 95% CI, 19.4–56.0), and the rate of clinical hepatitis was 20.0/100,000 person-years (95% CI, 11.8–39.9), rates that were 6.3 and 4.1 times greater than the reported rate during the same period, respectively.

Conclusions

In children younger than 5 years, the estimated infection rate was 13.8 times greater than the reported rate. Combined use of reported cases and results of seroprevalence surveys suggest that underreporting of HAV infection is substantial in Catalonia, especially in children younger than 5 years.

Introduction

Hepatitis A is an infection produced by the hepatitis A virus (HAV), a Hepatovirus belonging to the Picornaviridae family (1). HAV infection may be asymptomatic or lead to acute hepatitis, which generally is self-limiting, but the duration and severity increase with age 2, 3. Although most cases are benign, complications include fulminant hepatitis and death. Deaths from HAV infection are very infrequent in people younger than 40 years, but case-fatality rates are 2% in the 50- to 59-year age group and 13% in people older than 70 years (4).

Because of its epidemic potential 5, 6, the potential severity of the disease in adults (7), and the existence of an effective vaccine since the middle of the 1990s 8, 9, there is agreement that surveillance of hepatitis A is necessary 4, 10, 11.

One of the main difficulties in hepatitis A surveillance is determining the real incidence (12). Although physicians are obliged to report the disease to the health services in many countries, underreporting is common 13, 14 because the disease evolves and anicteric forms, with nonspecific clinical manifestations, are very frequent (6).

Seroprevalence studies of nonvaccinated subjects 15, 16 allow the proportion of infected people in different age groups to be estimated 17, 18, 19, 20, 21, but do not allow estimation of the frequency of new infections.

Integration of data collected from surveys of reported cases was suggested as an alternative to estimate the real incidence of an infectious disease 22, 23, 24.

The objective of this study is to estimate the incidence of HAV infection from available prevalence surveys and data on the reported incidence of clinical cases of hepatitis A in Catalonia.

Section snippets

Data Sources

Reporting of hepatitis A disease has been obligatory in Catalonia since 1990. All cases of hepatitis A reported to the Department of Health of the Generalitat of Catalonia between 1991 and 2003 were included, aggregating this information annually.

Prevalence data for HAV infection were obtained from seroprevalence studies carried out in Catalonia in 1989, 1996, and 2002 25, 26. Data from the 1989 study were used to estimate the incidence in 1991 to 1993; those from 1996, the incidence in 1994 to

Results

Figure 1 shows prevalence curves of HAV antibodies according to age groups for the 1989, 1996, and 2002 surveys. The prevalence in people 40 years or older was always more than 90%. In subjects younger than 40 years, a decrease in age-related prevalence was observed over time.

As listed in Table 1, the reported incidence rate for the study period was 4.9/100,000 person-years. The estimated rate of total infections was 31.1/100,000 person-years, and that of clinical infections, 20/100,000

Discussion

To decide which HAV vaccination strategy should be adopted, the intensity of both new infections and clinical cases of the disease must be determined.

In this study, the estimated incidence of clinical cases of hepatitis A was 20.0/100,000 person-years, and the rate of HAV infection was 31.1/100,000 person-years, values 4.1 and 6.3 times greater than the reported rate of 4.9/100,000 person-years, respectively.

Armstrong and Bell (28) found that the rate of the disease was 4.3 times the reported

References (52)

  • C.N. Shapiro et al.

    Epidemiology and risk group in the USA

    Vaccine

    (1992)
  • A. Dominguez et al.

    Effectiveness of a mass hepatitis A vaccination programme in preadolescents

    Vaccine

    (2003)
  • T. Samandari et al.

    Quantifying the impact of hepatitis A immunization in the United States, 1995-2001

    Vaccine

    (2004)
  • B.P. Bell et al.

    Hepatitis A virus

  • T.J. Harrison et al.

    Hepatitis viruses

  • C. Altman et al.

    Viral hepatitis A with prolonged course in adults

    Gastroenterol Clin Biol

    (1996)
  • N.S. Crowcroft et al.

    Guidelines for the control of hepatitis A virus infection

    Commun Dis Public Health

    (2001)
  • K. Nygard et al.

    Imported rocket salad partly responsible for increased incidence of hepatitis A cases in Sweden, 2000-2001

    Eurosurveillance

    (2001)
  • C.J. Staess et al.

    Sources of infection among persons with acute hepatitis A and no identified risk factors during a sustained community-wide outbreak

    Pediatrics

    (2000)
  • A. Bell et al.

    An outbreak of hepatitis A among young men associated with having sex in public venues

    Commun Dis Public Health

    (2001)
  • I. Kyrlagkitsis et al.

    Acute hepatitis A virus infection: A review of prognostic factors from 25 years experience in a tertiary referral center

    Hepatogastroenterology

    (2002)
  • E. Couturier et al.

    Surveillance de l'hepatitis A en France au cours des vingt dernières années: les donnes actuelles ne permettent pas d'estimer la vaux d'incidence

    Bul Epidemiol Hebdomadaire

    (2005)
  • Centers for Disease Control and Prevention

    Prevention of hepatitis A through active or passive immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP)

    MMWR Recomm Rep

    (1999)
  • E. Delarocque–Astagneau et al.

    Evaluation d'un systeme pilote de surveillance pour l'hepatite A, France 2001

    Bull Epidemiol Hebdomadaire

    (2005)
  • M.C. Morris et al.

    The changing epidemiological pattern of hepatitis A in England and Wales

    Epidemiol Infect

    (2002)
  • S. ElSaadany et al.

    Hepatitis A, B, and C in Canada. Results from the National Sentinel Health Unit Surveillance System, 1993-1995

    Can J Public Health

    (2002)
  • A. Dominguez et al.

    Prevalence of hepatitis A antibodies in schoolchildren in Catalonia (Spain) after the introduction of universal hepatitis A immunization

    J Med Virol

    (2004)
  • M.C. Morris-Cunnington et al.

    A population-based seroprevalence study of hepatitis A virus using oral fluid in England and Wales

    Am J Epidemiol

    (2004)
  • R.S. Koff

    Seroepidemiology of hepatitis A in the United States

    J Infect Dis

    (1995)
  • N.J. Gay et al.

    Age-specific antibody prevalence to hepatitis A in England: Implications for disease control

    Epidemiol Infect

    (1994)
  • M.E. Moschen et al.

    Hepatitis A infection: A seroepidemiological study in young adults in North-East Italy

    Eur J Epidemiol

    (1997)
  • W. Thierfelder et al.

    Prevalence of markers for hepatitis A, B and C in the German population. Results of the German National Health Interview and Examination Survey 1998

    Eur J Epidemiol

    (2001)
  • A.D. Fix et al.

    Age-specific prevalence of antibodies to hepatitis A in Santiago, Chile: Risk factors and shift in age of infection among children and young adults

    Am J Trop Med Hyg

    (2002)
  • N. Keiding

    Incidence-prevalence relationships

  • B.T. Grenfell et al.

    The estimation of age-related rates of infection from case notifications and serological data

    J Hyg (Lond)

    (1985)
  • C.J. Struchiner et al.

    Hepatitis A incidence rate estimates from a pilot seroprevalence survey in Rio de Janeiro, Brazil

    Int J Epidemiol

    (1999)
  • Cited by (0)

    This work was partially supported by a grant from the Fondo de Investigaciones Sanitarias, Instituto de Salud Carlos III (Red de Centros de Epidemiología y Salud Pública).

    View full text