Journal of Medical Virology 3897-101 (1992)
Current Seroepidemiology of Hepatitis D Virus Infection Among Hepatitis B Surface Antigen Carriers of General and High-Risk Populations in Taiwan Chien-Jen Chen, Su-Feng Tseng, Chih-Feng Lu, Hwa-Chen Lin, San-Lin You, Chang-Sheng Chen, Shih-Jen Hwang, Su-Fen Hsieh, and Shu-Tao Hsu Institute of Public Health, National Taiwan University College of Medicine (C.-J.C., S.-F.T., S.-L.Y.), Institute of Biomedical Sciences, Academia Sinica ( C . J . C . , S.-J.H.1, National Institute of Preventive Medicine, Department of Health, Executive Yuan, (C.-F.L., S.-T.H.), Taipei Municipal Center for Venereal Diseases Control (H.-C.L.), Taipei Municipal Anti-Narcotics Institute (C.-S.C.),Taipei and Department of Public Health, Kaohsiung Medical College, Kaohsiung (S.-F.H.1, Taiwan, Republic of China In order to assess the current seroepidemiology of hepatitis D virus (HDV) infection in Taiwan where hepatitis B virus (HBV) is hyperendemic, a total of 756 voluntary blood donors, 641 prostitutes, 1,014 patients with sexually transmitted diseases (STDs), and 628 drug abusers were studied. Radioimmunoassays were used for testing HBV infection markers and antibody against HDV (anti-HDV) among HBsAg carriers. The antiHDV prevalence among HBsAg carriers was significantly higher in STD patients (9.S0/0), prostitutes (33.1%), and drug abusers (68.1Y0) than in blood donors from the general population (2.2%).The prevalence gradually increased with age in blood donors and STD patients, but reached a plateau at a young age in prostitutes and drug abusers. Males had a higher prevalence than females in blood donors (2.7% vs. 01, STD patients (8.2% vs. 7.5%), and drug abusers (69.0%vs. 57.1%), but the difference was not statistically significant. STD patients with syphilis had a higher prevalence (19.5%) than those affected with non-ulcerating STDs (5.3%).While unlicensed prostitutes had a lower prevalence (1 3.6%) than licensed prostitutes (44.9%),intravenous drug abusers had a higher prevalence (73.1%) than non-intravenous drug abusers (34.6%). There was a twofold increase in antiHDV prevalence from 1986 to 1989 among prostitutes, but the prevalence remained unchanged in the general population and drug abusers. HDV infection remains limited to the high-risk groups and spread mainly by promiscuity and needle sharing in Taiwan. Q 1992 Wiley-Liss, Inc.
INTRODUCTION Taiwan is a n endemic area for hepatitis B virus (HBV) [Beasley et al., 1982; Chung e t al., 19881. In Taiwan, most HBV surface antigen (HBsAg) carriers are infected in early life [Chen et al., 19901, and approximately 40% of the HBsAg carriers can be attributed to perinatal transmission [Stevens et al., 19751. However, horizontal transmission by intra- and extra-familial infection routes is also important for transmission of HBV in Taiwan. The role of promiscuity and drug abuse in the determination of HBV infection in Taiwan has seldom been investigated. Hepatitis D virus (HDV) is a defective virus that may cause infection in the presence of active HBV [Rizzetto et al., 19771. Should HDV be introduced into the general susceptible population in Taiwan, the frequency of HDV infection may increase significantly. HDV infection, however, was reported to be infrequent in Taiwan with a prevalence of antibody against HDV (anti-HDV) of 6.1-8.0% among HBsAg-positive Chinese patients with chronic liver diseases before 1984 [Rizzetto et al., 1980; Chen et al., 1984; Govindarajan e t al., 19841. An increased antiHDV prevalence of 15.5% among patients with chronic liver disease was reported in 1987 [Wu and Tam, 19871. Asymptomatic HBsAg carriers had a much lower antiHDV prevalence than drug abusers and prostitutes [Chung et al., 1988; Wu and Tam, 1987; Lee et al., 1986; Chung e t al., 1989; Chen et al., 19881. Most of these studies were based on a small sample size, and factors associated with HDV infection were not examined in detail. This study was carried out to assess current epidemiological characteristics of HDV infection among HBsAg carriers of both general and high-risk populations in Taiwan.
KEY WORDS: hepatitis D virus, risk factor, vol-
Accepted for publication March 10, 1992. Address reprint requests to Chien-Jen Chen, Institute of Public Health, National Taiwan University College of Medicine, Jen-Ai Road Section 1, Taipei 10018, Taiwan, ROC.
untary blood donors 8 1992 WILEY-LISS, INC.
Chen et al.
98
S U B J E C T S AND METHODS S t u d y Subjects One thousand fourteen patients with sexually transmitted diseases (STDs),641 prostitutes, 628 drug abusers, and 756 voluntary blood donors were studied. All STD patients were recruited sequentially from the Taipei Municipal Center for Venereal Diseases Control during a period from February to May, 1989. By law, licensed prostitutes in Taiwan are examined routinely for major STDs and treated compulsorily if they are found to have disease. Unlicensed prostitutes arrested by the police were also examined mandatorily. Prostitutes were recruited into this study at the time of examination which was carried out in the Taipei Municipal Center for Venereal Diseases Control. There were 198, 231, and 212 prostitutes recruited in 1986, 1987, and 1989, respectively. Drug abusers were recruited from two different sources: the Taipei Municipal Anti-Narcotics Institute where drug abusers are institutionalized for withdrawal treatment, and the Yunlin Penitentiary where drug-related criminals are imprisoned. A total of 241 drug abusers were recruited from the Yunlin Penitentiary in February 1988, while 387 drug abusers were recruited from the Taipei Municipal AntiNarcotics Institute during a period from December 1988 to December 1989. Voluntary blood donors were also included in this study to compare HDV prevalence between high-risk groups and the general population in northern Taiwan. The Association of Voluntary Blood Donation in Taiwan has four district centers to provide island-wide service. HBV infection markers are tested routinely for donated blood samples at these centers. Those who donated the first blood sample in the Taipei Blood Donation Center and were found to be HBsAg-positive during August to September 1989 were recruited sequentially into this study. As the HDV prevalence reported previously was about 3% in the general population, only HBsAg-positive blood donors were included in order to increase the statistical power of the study. The mean 2 standard deviation of age was 27.4 2 7.8, 32.7 2 11.8, 32.9 2 9.5, and 36.7 2 10.3, respectively, for blood donors, STD patients, prostitutes, and drug abusers. There were more males than females among blood donors, STD patients, and drug abusers with a male-to-female ratio of 5.4,4.2, and 12.3, respectively. All prostitutes studied were female.
Serum Collection and L a b o r a t o r y Examination Blood samples collected from the study subjects were centrifuged to separate serum samples on the same day of blood collection. Serum specimens were stored at -30°C until serological examination. HBV infection markers including HBsAg, antibody against HBsAg, and antibody against HBV core antigen were tested in all serum samples by radioimmunoassay (RIA) using commercially available reagents ( Abbott Laboratories, North Chicago, IL). HBV e antigen, antibody against HBeAg, and antibody against HDV (anti-HDV) were
examined by RIA using commercial reagents ( Abbott Laboratories, North Chicago, IL) only for HBsAg-positive subjects whose serum samples were adequate for the tests. Samples were retested twice for HBV infection markers if they had a count per minute (CPM) value within the 10% of the cutoff value. Anti-HDV was also retested twice in samples with a CPM value within the 5% of the cutoff value. Specimens at borderline values were considered positive only if they were positive by two or three of these tests. All serum samples were examined blindly. R i s k Factors Risk factors associated with HDV infection were abstracted from institutional andlor medical records as well as obtained from standardized interviews according to a structured questionnaire. Sociodemographical characteristics including age, sex, ancestry, occupation, and/or educational level were obtained from all the study subjects. The diagnosis of STDs was obtained from medical records of the Taipei Municipal Center for Venereal Diseases Control for both prostitutes and STD patients. The information on working history was sought from prostitutes and the history of drug abuse was obtained from drug abusers by questionnaire interviews.
Statistical M e t h o d s Both prevalence rate and 95% confidence interval were calculated for HDV infection. Chi-square tests were used to examine the statistical significance of the difference in HDV prevalence among various groups categorized by nominal characteristics. Mantel-Haenszel chi-square tests were used to test the significance of a trend in HDV prevalence if compared groups were categorized by ordinal characteristics. Multiple binary regression analysis was also used to analyze multiple risk factors associated with the HDV infection. RESULTS HBV and HDV Infection R a t e The HBV infection prevalence (95% confidence interval) was 89.7% (87.9-91.6%), 98.1% (97.1-99.2%), and 97.9% (96.8-99.0%), respectively, among STD patients, prostitutes, and drug abusers. The corresponding figures for HBsAg carrier rate were 20.5% (18.0-23.0%), 20.3% (17.2-23.4%), and 29.0% (25.4-32.5%), respectively. The HBV infection rate was significantly higher among prostitutes and drug abusers than STD patients, while the HBsAg carrier rate in drug abusers was significantly higher than t h a t of STD patients and prostitutes. Table I shows the anti-HDV prevalence among HBsAg carriers in both general and high-risk populations. The anti-HDV prevalence was significantly different among blood donors (2.2%),STD patients (8.1%),prostitutes (34.6%), and drug abusers (68.5%).All the 95% confidence intervals of anti-HDV prevalence in these four groups did not overlap.
HDV Seroepidemiology in Taiwan TABLE I. Anti-HDV Prevalence Among HBsAg Carriers in General and Hinh-Risk Pouulations in Taiwan* Anti-HDV prevalencea Group No. Rate, % (95%C.I.), % General population 756 2.2 (1.2-3.3) Blood donors High-risk populations STD patients 210 8.1 (4.4-11.8) Prostitutes 133 34.6 (26.5-42.7) Drug abusers 178 68.5 (61.7-75.3) *Anti-HDV,antibodyagainst hepatitis D virus; HBsAg,hepatitis B surfaceantigen;STD,sexually transmitteddisease;C.I.,confidence interval. aThe prevalence was significantly different between any two groups based on chi-squaretests.
Risk Factors Associated With HDV Infection The relationship between the anti-HDV prevalence and sociodemographic characteristics among HBsAgpositive blood donors, STD patients, prostitutes, and drug abusers is shown in Table 11. The anti-HDV prevalence increased significantly with age up to 40 years and then declined slightly among blood donors and STD patients, but the prevalence reached a plateau at a young age in prostitutes and drug abusers. Males had a higher HDV prevalence than females among blood donors, STD patients, and drug abusers, but the difference was not statistically significant. There was no significant association between anti-HDV prevalence and ancestry, marital status, and occupation in the various groups. STD patients with syphilis had a significantly higher anti-HDV prevalence (19.5%)than patients affected with other non-ulcerating STDs (5.3%).Prostitutes currently affected with STDs had a higher prevalence (40%) than those without a current STD (30%),but the difference was not statistically significant. Table I11 shows the anti-HDV prevalence among HBsag-positive prostitutes by recruiting year and licensing status. There was a significant difference in antiHDV prevalence among prostitutes who were recruited in different years. An increase in prevalence was observed from 1986 to 1989. Unlicensed prostitutes had a significantly lower anti-HDV prevalence than licensed prostitutes. Anti-HDV prevalence among HBsAg-positive drug abusers by history of drug abuse is shown in Table IV. Intravenous drug abusers had a significantly higher anti-HDV prevalence than non-intravenous drug abusers. Neither starting age nor duration of drug abuse was associated significantly with anti-HDV prevalence. Institutionalization frequency was not related to anti-HDV prevalence. Multiple Binary Regression Analysis The associations between risk factors and anti-HDV prevalence were analyzed further by multiple binary regression analysis. The results remained similar to those of univariate analysis. In other words, a significant association with anti-HDV prevalence was observed for age among blood donors and STD patients, as
99
well as for syphilis among STD patients. Anti-HDV prevalence in prostitutes increased significantly from 1986 to 1989, and licensed prostitutes had a significantly higher prevalence than unlicensed prostitutes. A significantly higher anti-HDV prevalence was found among intravenous drug abusers than non-intravenous drug abusers.
DISCUSSION HBV is transmitted either perinatally or horizontally by body fluids. In Taiwan, the HBsAg carrier rate was as high as 15-2010 with a n HBV infection rate of 80-90% [Beasley et al., 1982; Chung et al., 19881. In this study, we observed a higher HBV infection rate among STD patients (95%confidence interval = 87.991.6%), prostitutes (97.1-99.2%), and drug abusers (96.8-99.0%) than in the general population. This suggests the importance of sexual transmission and needle sharing in horizontal transmission of HBV in Taiwan. However, a significantly higher HBsAg carrier rate was observed in drug abusers (25.4-32.5%) only. The HBsAg carrier rates in STD patients (18.0-23.0%) and prostitutes (17.2-23.4%)were not significantly different from that in the general population. It implies that most HBsAg carriers of both general and high-risk populations in Taiwan are infected in early childhood as reported previously [Chung et al., 1982; Chen et al., 19901. As a defective virus, HDV is transmitted with HBV by coinfection or superinfection. Routes of HDV transmission appear to be similar to those of HBV. However, HDV infection has been reported to be infrequent among patients with chronic liver diseases and asymptomatic HBsAg carriers in Taiwan. The anti-HDV prevalence among patients with chronic liver diseases was reported to be 7.5%in 1980 [Rizzetto et al., 19801, 6.1%[Chen et al., 19841, and 8.0% [Govindarajan et al., 19841 in 1984, as well as 15.5%in 1987 [Wu and Tam, 19871. The increase in anti-HDV prevalence among patients with chronic liver diseases was statistically significant. The anti-HDV prevalence of asymptomatic HBsAg carriers in the general population (2.2%)and HBsAg-positive drug abusers (73.1%)observed in this study was similar to that reported previously [Chung et al., 1988; Wu and Tam, 1987; Lee et al., 1986; Chung et al., 19891. A significant increase in anti-HDV prevalence among prostitutes from 1986 to 1989 was observed. The reasons for the recent increase in anti-HDV prevalence among certain subpopulations deserve further study. As in the case of HBV infection, the anti-HDV prevalence increased significantly in a gradient from blood donors, STD patients, prostitutes, to drug abusers. Both promiscuity and needle sharing seem to be major routes of HDV transmission in Taiwan. The anti-HDV prevalence was found to increase with age up to 40 years in blood donors and STD patients, but reaching a plateau at a young age in prostitutes and drug abusers who had a much higher risk of infection by body fluid-transmitted viruses.
100
Chen et al. TABLE 11. Anti-HDV Prevalence in HBsAg-Positive Blood Donors, STD Patients, Prostitutes, and Drug Abusers by Sociodemographic Characteristics* Anti-HDV prevalence, % Blood STD Drug Variable Group donors patients Prostitutes abusers Age Sex Ancestry Occupation
Marital status
Current Seroepidemiology of Hepatitis D Virus Infection Among Hepatitis B Surface Antigen Carriers of General and High-Risk Populations in Taiwan Chien-Jen Chen, Su-Feng Tseng, Chih-Feng Lu, Hwa-Chen Lin, San-Lin You, Chang-Sheng Chen, Shih-Jen Hwang, Su-Fen Hsieh, and Shu-Tao Hsu Institute of Public Health, National Taiwan University College of Medicine (C.-J.C., S.-F.T., S.-L.Y.), Institute of Biomedical Sciences, Academia Sinica ( C . J . C . , S.-J.H.1, National Institute of Preventive Medicine, Department of Health, Executive Yuan, (C.-F.L., S.-T.H.), Taipei Municipal Center for Venereal Diseases Control (H.-C.L.), Taipei Municipal Anti-Narcotics Institute (C.-S.C.),Taipei and Department of Public Health, Kaohsiung Medical College, Kaohsiung (S.-F.H.1, Taiwan, Republic of China In order to assess the current seroepidemiology of hepatitis D virus (HDV) infection in Taiwan where hepatitis B virus (HBV) is hyperendemic, a total of 756 voluntary blood donors, 641 prostitutes, 1,014 patients with sexually transmitted diseases (STDs), and 628 drug abusers were studied. Radioimmunoassays were used for testing HBV infection markers and antibody against HDV (anti-HDV) among HBsAg carriers. The antiHDV prevalence among HBsAg carriers was significantly higher in STD patients (9.S0/0), prostitutes (33.1%), and drug abusers (68.1Y0) than in blood donors from the general population (2.2%).The prevalence gradually increased with age in blood donors and STD patients, but reached a plateau at a young age in prostitutes and drug abusers. Males had a higher prevalence than females in blood donors (2.7% vs. 01, STD patients (8.2% vs. 7.5%), and drug abusers (69.0%vs. 57.1%), but the difference was not statistically significant. STD patients with syphilis had a higher prevalence (19.5%) than those affected with non-ulcerating STDs (5.3%).While unlicensed prostitutes had a lower prevalence (1 3.6%) than licensed prostitutes (44.9%),intravenous drug abusers had a higher prevalence (73.1%) than non-intravenous drug abusers (34.6%). There was a twofold increase in antiHDV prevalence from 1986 to 1989 among prostitutes, but the prevalence remained unchanged in the general population and drug abusers. HDV infection remains limited to the high-risk groups and spread mainly by promiscuity and needle sharing in Taiwan. Q 1992 Wiley-Liss, Inc.
INTRODUCTION Taiwan is a n endemic area for hepatitis B virus (HBV) [Beasley et al., 1982; Chung e t al., 19881. In Taiwan, most HBV surface antigen (HBsAg) carriers are infected in early life [Chen et al., 19901, and approximately 40% of the HBsAg carriers can be attributed to perinatal transmission [Stevens et al., 19751. However, horizontal transmission by intra- and extra-familial infection routes is also important for transmission of HBV in Taiwan. The role of promiscuity and drug abuse in the determination of HBV infection in Taiwan has seldom been investigated. Hepatitis D virus (HDV) is a defective virus that may cause infection in the presence of active HBV [Rizzetto et al., 19771. Should HDV be introduced into the general susceptible population in Taiwan, the frequency of HDV infection may increase significantly. HDV infection, however, was reported to be infrequent in Taiwan with a prevalence of antibody against HDV (anti-HDV) of 6.1-8.0% among HBsAg-positive Chinese patients with chronic liver diseases before 1984 [Rizzetto et al., 1980; Chen et al., 1984; Govindarajan e t al., 19841. An increased antiHDV prevalence of 15.5% among patients with chronic liver disease was reported in 1987 [Wu and Tam, 19871. Asymptomatic HBsAg carriers had a much lower antiHDV prevalence than drug abusers and prostitutes [Chung et al., 1988; Wu and Tam, 1987; Lee et al., 1986; Chung e t al., 1989; Chen et al., 19881. Most of these studies were based on a small sample size, and factors associated with HDV infection were not examined in detail. This study was carried out to assess current epidemiological characteristics of HDV infection among HBsAg carriers of both general and high-risk populations in Taiwan.
KEY WORDS: hepatitis D virus, risk factor, vol-
Accepted for publication March 10, 1992. Address reprint requests to Chien-Jen Chen, Institute of Public Health, National Taiwan University College of Medicine, Jen-Ai Road Section 1, Taipei 10018, Taiwan, ROC.
untary blood donors 8 1992 WILEY-LISS, INC.
Chen et al.
98
S U B J E C T S AND METHODS S t u d y Subjects One thousand fourteen patients with sexually transmitted diseases (STDs),641 prostitutes, 628 drug abusers, and 756 voluntary blood donors were studied. All STD patients were recruited sequentially from the Taipei Municipal Center for Venereal Diseases Control during a period from February to May, 1989. By law, licensed prostitutes in Taiwan are examined routinely for major STDs and treated compulsorily if they are found to have disease. Unlicensed prostitutes arrested by the police were also examined mandatorily. Prostitutes were recruited into this study at the time of examination which was carried out in the Taipei Municipal Center for Venereal Diseases Control. There were 198, 231, and 212 prostitutes recruited in 1986, 1987, and 1989, respectively. Drug abusers were recruited from two different sources: the Taipei Municipal Anti-Narcotics Institute where drug abusers are institutionalized for withdrawal treatment, and the Yunlin Penitentiary where drug-related criminals are imprisoned. A total of 241 drug abusers were recruited from the Yunlin Penitentiary in February 1988, while 387 drug abusers were recruited from the Taipei Municipal AntiNarcotics Institute during a period from December 1988 to December 1989. Voluntary blood donors were also included in this study to compare HDV prevalence between high-risk groups and the general population in northern Taiwan. The Association of Voluntary Blood Donation in Taiwan has four district centers to provide island-wide service. HBV infection markers are tested routinely for donated blood samples at these centers. Those who donated the first blood sample in the Taipei Blood Donation Center and were found to be HBsAg-positive during August to September 1989 were recruited sequentially into this study. As the HDV prevalence reported previously was about 3% in the general population, only HBsAg-positive blood donors were included in order to increase the statistical power of the study. The mean 2 standard deviation of age was 27.4 2 7.8, 32.7 2 11.8, 32.9 2 9.5, and 36.7 2 10.3, respectively, for blood donors, STD patients, prostitutes, and drug abusers. There were more males than females among blood donors, STD patients, and drug abusers with a male-to-female ratio of 5.4,4.2, and 12.3, respectively. All prostitutes studied were female.
Serum Collection and L a b o r a t o r y Examination Blood samples collected from the study subjects were centrifuged to separate serum samples on the same day of blood collection. Serum specimens were stored at -30°C until serological examination. HBV infection markers including HBsAg, antibody against HBsAg, and antibody against HBV core antigen were tested in all serum samples by radioimmunoassay (RIA) using commercially available reagents ( Abbott Laboratories, North Chicago, IL). HBV e antigen, antibody against HBeAg, and antibody against HDV (anti-HDV) were
examined by RIA using commercial reagents ( Abbott Laboratories, North Chicago, IL) only for HBsAg-positive subjects whose serum samples were adequate for the tests. Samples were retested twice for HBV infection markers if they had a count per minute (CPM) value within the 10% of the cutoff value. Anti-HDV was also retested twice in samples with a CPM value within the 5% of the cutoff value. Specimens at borderline values were considered positive only if they were positive by two or three of these tests. All serum samples were examined blindly. R i s k Factors Risk factors associated with HDV infection were abstracted from institutional andlor medical records as well as obtained from standardized interviews according to a structured questionnaire. Sociodemographical characteristics including age, sex, ancestry, occupation, and/or educational level were obtained from all the study subjects. The diagnosis of STDs was obtained from medical records of the Taipei Municipal Center for Venereal Diseases Control for both prostitutes and STD patients. The information on working history was sought from prostitutes and the history of drug abuse was obtained from drug abusers by questionnaire interviews.
Statistical M e t h o d s Both prevalence rate and 95% confidence interval were calculated for HDV infection. Chi-square tests were used to examine the statistical significance of the difference in HDV prevalence among various groups categorized by nominal characteristics. Mantel-Haenszel chi-square tests were used to test the significance of a trend in HDV prevalence if compared groups were categorized by ordinal characteristics. Multiple binary regression analysis was also used to analyze multiple risk factors associated with the HDV infection. RESULTS HBV and HDV Infection R a t e The HBV infection prevalence (95% confidence interval) was 89.7% (87.9-91.6%), 98.1% (97.1-99.2%), and 97.9% (96.8-99.0%), respectively, among STD patients, prostitutes, and drug abusers. The corresponding figures for HBsAg carrier rate were 20.5% (18.0-23.0%), 20.3% (17.2-23.4%), and 29.0% (25.4-32.5%), respectively. The HBV infection rate was significantly higher among prostitutes and drug abusers than STD patients, while the HBsAg carrier rate in drug abusers was significantly higher than t h a t of STD patients and prostitutes. Table I shows the anti-HDV prevalence among HBsAg carriers in both general and high-risk populations. The anti-HDV prevalence was significantly different among blood donors (2.2%),STD patients (8.1%),prostitutes (34.6%), and drug abusers (68.5%).All the 95% confidence intervals of anti-HDV prevalence in these four groups did not overlap.
HDV Seroepidemiology in Taiwan TABLE I. Anti-HDV Prevalence Among HBsAg Carriers in General and Hinh-Risk Pouulations in Taiwan* Anti-HDV prevalencea Group No. Rate, % (95%C.I.), % General population 756 2.2 (1.2-3.3) Blood donors High-risk populations STD patients 210 8.1 (4.4-11.8) Prostitutes 133 34.6 (26.5-42.7) Drug abusers 178 68.5 (61.7-75.3) *Anti-HDV,antibodyagainst hepatitis D virus; HBsAg,hepatitis B surfaceantigen;STD,sexually transmitteddisease;C.I.,confidence interval. aThe prevalence was significantly different between any two groups based on chi-squaretests.
Risk Factors Associated With HDV Infection The relationship between the anti-HDV prevalence and sociodemographic characteristics among HBsAgpositive blood donors, STD patients, prostitutes, and drug abusers is shown in Table 11. The anti-HDV prevalence increased significantly with age up to 40 years and then declined slightly among blood donors and STD patients, but the prevalence reached a plateau at a young age in prostitutes and drug abusers. Males had a higher HDV prevalence than females among blood donors, STD patients, and drug abusers, but the difference was not statistically significant. There was no significant association between anti-HDV prevalence and ancestry, marital status, and occupation in the various groups. STD patients with syphilis had a significantly higher anti-HDV prevalence (19.5%)than patients affected with other non-ulcerating STDs (5.3%).Prostitutes currently affected with STDs had a higher prevalence (40%) than those without a current STD (30%),but the difference was not statistically significant. Table I11 shows the anti-HDV prevalence among HBsag-positive prostitutes by recruiting year and licensing status. There was a significant difference in antiHDV prevalence among prostitutes who were recruited in different years. An increase in prevalence was observed from 1986 to 1989. Unlicensed prostitutes had a significantly lower anti-HDV prevalence than licensed prostitutes. Anti-HDV prevalence among HBsAg-positive drug abusers by history of drug abuse is shown in Table IV. Intravenous drug abusers had a significantly higher anti-HDV prevalence than non-intravenous drug abusers. Neither starting age nor duration of drug abuse was associated significantly with anti-HDV prevalence. Institutionalization frequency was not related to anti-HDV prevalence. Multiple Binary Regression Analysis The associations between risk factors and anti-HDV prevalence were analyzed further by multiple binary regression analysis. The results remained similar to those of univariate analysis. In other words, a significant association with anti-HDV prevalence was observed for age among blood donors and STD patients, as
99
well as for syphilis among STD patients. Anti-HDV prevalence in prostitutes increased significantly from 1986 to 1989, and licensed prostitutes had a significantly higher prevalence than unlicensed prostitutes. A significantly higher anti-HDV prevalence was found among intravenous drug abusers than non-intravenous drug abusers.
DISCUSSION HBV is transmitted either perinatally or horizontally by body fluids. In Taiwan, the HBsAg carrier rate was as high as 15-2010 with a n HBV infection rate of 80-90% [Beasley et al., 1982; Chung et al., 19881. In this study, we observed a higher HBV infection rate among STD patients (95%confidence interval = 87.991.6%), prostitutes (97.1-99.2%), and drug abusers (96.8-99.0%) than in the general population. This suggests the importance of sexual transmission and needle sharing in horizontal transmission of HBV in Taiwan. However, a significantly higher HBsAg carrier rate was observed in drug abusers (25.4-32.5%) only. The HBsAg carrier rates in STD patients (18.0-23.0%) and prostitutes (17.2-23.4%)were not significantly different from that in the general population. It implies that most HBsAg carriers of both general and high-risk populations in Taiwan are infected in early childhood as reported previously [Chung et al., 1982; Chen et al., 19901. As a defective virus, HDV is transmitted with HBV by coinfection or superinfection. Routes of HDV transmission appear to be similar to those of HBV. However, HDV infection has been reported to be infrequent among patients with chronic liver diseases and asymptomatic HBsAg carriers in Taiwan. The anti-HDV prevalence among patients with chronic liver diseases was reported to be 7.5%in 1980 [Rizzetto et al., 19801, 6.1%[Chen et al., 19841, and 8.0% [Govindarajan et al., 19841 in 1984, as well as 15.5%in 1987 [Wu and Tam, 19871. The increase in anti-HDV prevalence among patients with chronic liver diseases was statistically significant. The anti-HDV prevalence of asymptomatic HBsAg carriers in the general population (2.2%)and HBsAg-positive drug abusers (73.1%)observed in this study was similar to that reported previously [Chung et al., 1988; Wu and Tam, 1987; Lee et al., 1986; Chung et al., 19891. A significant increase in anti-HDV prevalence among prostitutes from 1986 to 1989 was observed. The reasons for the recent increase in anti-HDV prevalence among certain subpopulations deserve further study. As in the case of HBV infection, the anti-HDV prevalence increased significantly in a gradient from blood donors, STD patients, prostitutes, to drug abusers. Both promiscuity and needle sharing seem to be major routes of HDV transmission in Taiwan. The anti-HDV prevalence was found to increase with age up to 40 years in blood donors and STD patients, but reaching a plateau at a young age in prostitutes and drug abusers who had a much higher risk of infection by body fluid-transmitted viruses.
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Chen et al. TABLE 11. Anti-HDV Prevalence in HBsAg-Positive Blood Donors, STD Patients, Prostitutes, and Drug Abusers by Sociodemographic Characteristics* Anti-HDV prevalence, % Blood STD Drug Variable Group donors patients Prostitutes abusers Age Sex Ancestry Occupation
Marital status
