Hepatitis B virus (HBV) and hepatitis C virus (HCV) infection with parenteral mode of transmission have spread widely in Estonia, primarily in the North-Eastern and Northern (including Tallinn, the capital) regions over the last decade (Fig. 1). This increase is characterized not only by the high number of acute cases, but also a clear increase in the number of estimated chronic viral hepatitis.
In Estonia, the incidence rate of acute hepatitis B during the 1980s and early 1990s was on average 11.7 per 100 000 population (range 7.0-15.8). Notification of HCV infection, based on HCV antibody detection was first implemented in Estonia in 1991. Incidence rates for HCV infection in the early and mid 1990s ranged from 0.4 to 4.4 per 100 000 population.
The objective is to provide an overview of the current epidemiological situation and trends for viral hepatitis B and C infection in Estonia.
Epidemiological data were obtained through surveillance of reported hepatitis B and hepatitis C virus infection (1, 2, 3). Hospitals and family doctors notified laboratory confirmed cases of hepatitis B and C to the Estonian Health Protection Inspectorate.
The prevalence of HBV and HCV was studied in three groups of injecting drug users (IDUs). The first group consisted of 237 prisoners from Tallinn Central Prison (all HIV negative). The second group included 100 persons visiting Anonymous consulting rooms in Northern Estonia (17 of whom were HIV positive). The third group of 122 inmates (all HIV positive) was from Tallinn Central Prison. Participants were from 15-50 years of age and the male to female ratio was 9:1. The surveys were carried out in 1996-2000 and 2002-2003.
Results and discussion
Epidemiological situation and trends
The population of Estonia is about 1.4 million and distributed unequally through the country. The Northern and North-Eastern regions (close to the border of the Russian Federation) are the most urbanised and densely populated parts in Estonia. The rapid spread of hepatitis B and C started in 1996-1997 with 90% of all registered cases in the country from these parts of Estonia.
The reported incidence of acute hepatitis B infection was 2.9 times higher and the incidence of hepatitis C virus infection 4.7 times higher in 2001 than in 1995, being 32.8 and 22.4 per 100 000 population, respectively. However, the incidence has decreased during the last two years (Fig. 1). Thus, the incidence of hepatitis B per 100 000 decreased from 17.8 in 2002 to 12.8 in 2003, and the incidence of hepatitis C from 14.6 in 2002 to 11.4 in 2003.
Some changes have been observed in the age structure and routes of transmission for these infections during last years. The incidence of HBV and HCV infection is highest among persons aged 15-19 and 20-29 years (Table 1) and in general is higher among men.
Several risk factors for HBV and HCV infection are well established. In Estonia, HBV and HCV transmission via blood transfusion and medical procedures has declined significantly during the last decade while risk factors other than transfusion were recognized as the most important (Table 2). Currently, injection drug use is the most common risk factor identified among youth, accounting for more than half of all new hepatitis cases. The route of transmission for approximately 40% of the cases remains unknown.
Chronic hepatitis B, chronic hepatitis C and chronic hepatitis of unknown etiology have been notifiable since 1998 in Estonia. Thus, the proportion of cases with chronic hepatitis increased from 6.8% in 1998 to 34.5% in 2002 among all notified cases of viral hepatitis. This increase might be explained by both improvement of the surveillance system and an absolute increase of chronic hepatitis in the population.
The main etiological agent for chronic hepatitis was hepatitis C virus, comprising about 70% of all reported cases in 1998-2002. Injection drug use was identified as the main risk factor with the majority of cases among persons 15-29 years of age.
Seroprevalence data of high-risk groups
Viral hepatitis is a significant cause of morbidity among injecting drug users. Concurrent infections with multiple hepatitis viruses and other blood-borne pathogens such as human immunodeficiency virus (HIV) are common among IDUs. Chronically infected IDUs are major reservoirs of HBV and HCV and may transmit the infections to the general population.
In Estonia, the rapid increase in intravenous drug use started in 1994-1995 and remains at a high level with no decrease until now. There is an estimated 12 000-17 000 IDUs in the country. IDUs are mostly heroin users, about 85% of them Russian-speaking and 75% are males aged 15-25 years. As a result, some communities are especially vulnerable to the spread of hepatitis B and C as well as HIV infection (4). The spread of viral hepatitis preceded the concentrated epidemic of HIV in 2000-2003 among IDUs in North-Eastern and Northern Estonia (5, 6). The incidence rate of HIV infection remains high for today.
According to data of the Virology Department at the National Institute of Health Development (NIHD) in 2002-2003, 65% of IDUs (persons visiting Anonymous consulting facilities in Tallinn and the North-Eastern county) were seropositive for HBV and 90% for HCV. In general, HBV and HCV co-infection is common among drug users. The rate of co-infection among studied IDUs was 65% (7).
A large number of prisoners in Estonia are at risk of contracting hepatitis B and C infection as a result of sharing syringes and unhygienic tattooing. It has been estimated that about 30% of Estonian prisoners are injecting drugs.
The study of 237 imprisoned IDUs indicated that the prevalence of HBV and HCV in 1996-2000 was 82% and 94%, respectively. Eighty-six percent of HCV infected IDUs were found to have some marker of HBV infection. HBV and HCV infection was detected among 20.0% and 12.5% of non drug-dependent inmates (n=40), respectively (unpublished data, NIHD Virology Department). Among blood donors in Estonia the prevalence of HBV and HCV is on average 0.1% and 0.3 %, respectively.
In a recent survey (2002-2003)*, the prevalence of HBV (89.3%) and HCV (97.5%), as well as of HBV+HCV co-infection (88.5%) was found to be significantly higher in imprisoned HIV-positive IDUs than among those visiting Anonymous consulting rooms.
Markers of current chronic HBV infection were detected among 8.1% of studied imprisoned IDUs, who were not clinically ill (8). Data for chronic hepatitis C infection are not available.
Taking into account the current epidemiological situation for viral hepatitis in Estonia, there is an urgent need for preventive measures. Behavioral interventions to reduce the harm and risk of HBV/HCV infections, HBV vaccination, and appropriate medical management of chronically infected persons from the community at large and IDUs population could help to solve this serious public health problem in Estonia. Because there is no preventive HCV vaccine, primary prevention is the only way to halt the spread of HCV.
HBV vaccination is free of charge for some groups including health-care workers (from 1997), adolescents at the age of 13 years (from 1999) and newborns throughout the country (from 2003). Efforts to vaccinate adults (including IDUs and prisoners) have been limited, primarily due to the absence of sustainable programs and vaccine cost.
In 2002-2003, Danish researchers from Odense University Hospital and the Estonian Ministry of Justice conducted a cooperative project. In this study, compliance to an accelerated (0, 1 and 3 weeks) compared to the standard (0, 1 and 6 months) schedule for prophylactic hepatitis B vaccination among IDUs imprisoned in Tallinn Central Prison was investigated. The full course of vaccination (three times) was administrated to 457 IDUs (81%) of 566 inmates included in the study. The results revealed that a short hepatitis B vaccination schedule among imprisoned IDUs has a significantly higher compliance and seroprotection rate than the standard six months schedule and should therefore be recommended for use in this population. Low seroprotection rate was correlated to concurrent hepatitis C infection (9).
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