Hepatitis D virus infection among intravenous drug abusers in Taiwan: analysis of risk factors and liver function tests

To investigate the prevalence of hepatitis D virus (HDV) and hepatitis B virus (HBV) infection among intravenous drug abusers in Taiwan, a total of 761 male prisoners, including 680 intravenous drug abusers, were studied for serological markers of HBV and HDV. Questionnaires were distributed to evaluate the risk factors for HDV infection and also to estimate the strength of association among HDV infection and the risk factors. HBV infection was common, and the positive rates of HBV markers between intravenous drug abusers and non-drug abusers were not statistically different. However, the positive rate of the antibody to HDV was significantly higher among intravenous drug abusers than among non-drug abusers (21.3% vs. 8.6%). Of 131 chronic HBV carriers with intravenous drug abuse, 119 (91%) were anti-HD positive. Using multiple logistic regression models, we found that the most important risk factor for HDV infection was hepatitis B surface antigen (HBsAg) carriage, and intravenous drug addiction the next. A matched case-control study also was conducted to compare liver function tests among both anti-HD- and HBsAg-positive group anti-HD-negative, and HBs-AG-positive group as well as those with neither positive. Statistically significant difference in liver function tests was not found. It is concluded that the HBsAg carriers with intravenous drug abuse in Taiwan are commonly HDV infected with and that the infection does not seem to affect the liver as assessed by liver function tests.     

Seroepidemiology of hepatitis B virus, hepatitis D virus, and human immunodeficiency virus infections among parenteral drug abusers in southern Taiwan

A total of 390 parenteral drug abusers (PDAs) at the Kaohsiung Municipal Narcotics Abstention Institute were examined for markers of hepatitis B virus (HBV), hepatitis D virus (HDV), and human immunodeficiency virus (HIV). All sera were tested for hepatitis B surface antigen (HBsAg), surface antibody (anti-HBs), and core antibody (anti-HBc) by radioimmunoassay (RIA) and for antibody to HIV (anti-HIV) by enzyme-linked immunosorbent assay (ELISA). Hepatitis B e antigen (HBeAg) and antibody to HDV (anti-HDV) were also tested for HBsAg-positive serum samples. Although the HBsAg-positive rate (22.1%) among PDAs was similar to that of the general population in southern Taiwan, the HBV infection rate (99.2%) and the anti-HDV-positive rate (78.5%) among HBsAg-positive subjects were significantly higher than those of the general population in southern Taiwan (P less than 0.0001). None of the PDAs studied were positive for anti-HIV. The levels of serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) among PDAs were significantly higher than those of the general population in southern Taiwan (P less than 0.0001). The more frequent the institutionalisation, the higher the infection rates with HBV and HDV and elevated levels of SGOT and SGPT. Horizontal transmission through parenteral drug abuse may be considered a possible reason for the significantly higher rates of HBV and HDV among parenteral drug abusers.     

Antibodies to hepatitis delta virus in intravenous drug addicts and male homosexuals in Spain

In a study to determine the incidence of infection with hepatitis delta virus (HDV) in high-risk groups in Spain, tests to detect serological markers of infection with hepatitis B virus (HBV) and total antibodies against HDV (anti-HDV) were performed in serum samples from 451 unselected intravenous drug addicts and 168 homosexual or bisexual men. Most samples were obtained from primary health care units in Madrid. In drug addicts 87.4% of samples were positive for HBV markers and 15.1% were positive for anti-HDV. However, the incidence of anti-HD was much higher in HBsAg carriers (70.7%) than in individuals positive for anti-HBs (10.4%). Ninety-two samples (54.8%) from homosexual men were positive for HBV markers, but all were negative for anti-HD. Thus, parenteral transmission seems to play a major role in the spread of HDV in Spain, the sexual route being of minor relevance.     

Diagnostic significance of IgM antibody to hepatitis delta virus in fulminant hepatitis B

The prevalence of hepatitis delta virus (HDV) infection was studied in 25 adult patients with fulminant hepatitis who were admitted consecutively to our unit from February, 1986, to September, 1988. Enzyme and radioimmunoassays were used for the detection of serological markers of HAV, HBV, and HDV (HDAg, IgM anti-HD, total [IgG] anti-HD) infections. Two hundred twenty-nine serum samples (three to 19 samples/patient) were tested for serological markers of HDV infection. Of the 25 patients, 17 (68%) were HBsAg-positive, and the remaining eight (32%) were HBsAg-negative on admission to the hospital. All patients were seropositive for IgM anti-HBc. Serological markers of HDV infection were detected in 13 (52%) of the 25 patients. In particular, HDV infection was observed in nine (53%) of the 17 HBsAg-positive and in four (50%) of the eight HBsAg-negative patients with type B fulminant hepatitis. Survival was 16.7% for patients with hepatitis B and 57.8% for patients with B and D coinfection. Coinfections were responsible for fulminant hepatitis in 100% of drug addicts and 40% in patients who were not drug addicts. All patients with HBV/HDV coinfections became seropositive for IgM anti-HD. The results show that HDV infection has a significant role (52%) in type B fulminant hepatitis in an area with a moderate prevalence of HBV infections, that it should be tested in cases with early clearance of HBsAg, and that it does not seem to be accompanied by a high fatality rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Current seroepidemiology of hepatitis D virus infection among hepatitis B surface antigen carriers of general and high-risk populations in Taiwan.

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 anti-HDV prevalence among HBsAg carriers was significantly higher in STD patients (9.6%), prostitutes (33.1%), and drug abusers (68.1%) 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. 0), 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 (13.6%) 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 anti-HDV 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.     

Influence of hepatitis delta virus superinfection on the clearance of hepatitis B virus (HBV) markers in HBV carriers in Japan

To elucidate the influence of hepatitis delta virus (HDV) superinfection on the clearance of hepatitis B virus (HBV) associated antigens in HBV carriers, we examined for antibody to hepatitis delta antigen (anti-HD) serial sera collected from 1,029 HBV carriers in Kure, Japan. Of the 242 HBV carriers with hepatitis B e antigen (HBeAg), 28 became seropositive for anti-HD, of whom 18 (64.3%) cleared HBeAg; 214 did not become seropositive for anti-HD, of whom 70 (32.7%) cleared HBeAg. Thus, HBeAg clearance was observed in a significantly higher proportion of HDV-superinfected carriers as compared with carriers without HDV infection (P less than 0.005). In the 56 HBV carriers who cleared hepatitis B surface antigen (HBsAg), anti-HD was detected in three cases with increased serum alanine aminotransferase activity preceding HBsAg clearance. The duration of anti-HD seropositive state was less than 5 years, and the titer of anti-HD was relatively low in every case. These data suggest that the HDV infection rate in Japan is higher than previously reported, that HDV superinfection can be one of the factors that induce the HBeAg clearance and HBsAg clearance in HBV carriers, and also that the most likely outcome of HDV superinfection in HBV carriers in Japan may be acute self-limited infection.     

Serological diagnosis of acute delta hepatitis

Sixty-three intravenous drug addicts with HBsAg positive hepatitis were studied to evaluate the diagnostic usefulness of hepatitis delta virus (HDV) markers for diagnosis of acute HDV infection. Patients were tested for HBsAg, anti-HBc-IgM, and anti-HD-IgM by radioimmunoassay (RIA), and for hepatitis delta antigen (HD-Ag) by a commercial enzyme-linked immunoassay (ELISA). At least two serum samples at a mean interval of 4 wk were examined from each patient. HDV markers were found in 41 cases. In the first serum sample (obtained within 1-5 wk after onset of illness) HD-Ag was found in 32 cases and was the only HDV marker in 22; in the remaining 10 cases, HD-Ag was found along with total anti-HD, and in 6 of them anti-HD-IgM was also detected. Five additional patients were only positive for total anti-HD, and anti-HD of the IgM class was the only marker in one patient. HD-Ag was found more often in the patients studied during the first 2 wk of illness. In the second serum sample, HD-Ag was never the only marker detected, seven patients were still positive, and in all of them anti-HD was also present. Thirty patients were only positive for anti-HD. Seroconversion from HD-Ag to anti-HD occurred in 20 of 22 (91%) patients. The results suggest that HD-Ag determination by ELISA in the initial serum sample, during the first 2 wk of illness, may be the most sensitive test for the diagnosis of acute delta infection, and that seroconversion to anti-HD usually occurs after the sixth week of illness.     

重型病毒性肝炎中丁型肝炎病毒的检测

为了探讨丁型肝炎病毒（ＨＤＶ）感染在重型病毒性肝炎中的作用，对北京佑安医院１９８０年至１９８９年收治的５４例急性和亚急性重型肝炎和３８例急性乙肝患者血清，应用国产ＨＤＶＥＬＩＳＡ试剂测定抗－ＨＤ、抗－ＨＤＩｇＭ和ＨＤＡｇ，应用斑点杂交技术测定ＨＤＶＲＮＡ。结果发现重型肝炎组ＨＯＶ－Ｍ检出率明显高于急性乙肝组（２７．８％比５．３％．Ｐ＜０．０５）。单独ＨＢＶ感染和ＨＤＶ／ＨＢＶ混合感染的重型肝炎患者均有较高的病死率。提示ＨＤＶ感染是重型肝炎中重要的病原学因素之一，ＨＤＶ与ＨＢＶ具有协同作用加重肝损害，导致肝衰竭。     

Prevalence and clinical significance of hepatitis D virus co-infection in patients with chronic hepatitis B in Korea

Hepatitis D virus (HDV) infection can cause severe acute and chronic liver disease in patients infected with hepatitis B virus (HBV). Despite the significant decline in the global HDV infection, it remains a major health concern in some countries. This study aimed to investigate the prevalence and clinical features of HDV co-infection in patients with chronic HBV infection in Korea, where HBV infection is endemic. Nine hundred forty patients [median age, 48 (18-94) years; men, 64.5%] infected chronically with HBV were enrolled consecutively. All patients who were positive for hepatitis B surface antigen (HBsAg) for at least 6 months and were tested for anti-HDV. A portion of the HDV delta antigen was amplified, sequenced, and subjected to molecular and phylogenetic analysis using sera from the patients who were anti-HDV positive. Clinical features and virologic markers were evaluated. Inactive HBsAg carriers, chronic hepatitis B, cirrhosis and hepatocellular carcinoma accounted for 29.5%, 44.7%, 17.9%, and 8.0%, respectively. Only three patients were positive for anti-HDV, corresponding to a 0.32% positive rate. All patients who were positive for anti-HDV were inactive HBsAg carriers. HDV RNA could be amplified by PCR from the sera of two patients. Phylogenetic analysis showed that both carried HDV genotype 1. In conclusion, the prevalence of HDV infection is very low (0.32%) in Korea. All HDVs were genotype 1 and detected in inactive HBsAg carriers. Therefore, HDV co-infection may not have a significant clinical impact in Korean patients with chronic HBV infection.     

Co-expression of markers for hepatitis delta and hepatitis B viruses in human liver

Delta hepatitis (HDV) infection can only occur in the presence of hepatitis B (HBV) infection, as HDV requires a coat of HBV surface antigen (HBsAg) for assembly of complete virus. A number of studies have examined the variation of HBV markers in serum and liver during establishment of HDV infection, but none has systematically examined the relationship between the two viruses in individual hepatocytes. Liver biopsies from five patients with HDV/HBV infection were stained for HBsAg, HBV core antigen (HBcAg) and hepatitis D (delta) antigen (HDAg). Double immunostaining was performed with a combination of indirect immunoperoxidase and alkaline phosphatase/antialkaline phosphatase techniques. HDV and HBV antigens were expressed in all five liver biopsies. Co-localization of HBsAg was seen in up to 39% of HDAg positive cells, and HBcAg in up to 8% of HDAg positive cells. HBcAg was detectable in approximately 9% of HBsAg positive cells, and HBsAg in approximately 12% of HBcAg positive cells. HDV can replicate without HBV but ultimately requires HBV to produce complete virus and subsequently infect other cells. In this study the majority of HDV positive cells did not appear to contain HBV markers. This might suggest delta virus replication without assembly, or possibly sequential production/assembly of the virus.     

Host dependent modulation of hepatitis delta virus replication in chronic delta hepatitis.

To determine whether host dependent differences modulated hepatitis delta virus replication in chronic delta hepatitis, we tested HDV RNA in homosexual and intravenous drug abuser populations. Overall, the seroprevalence of HDV RNA in the two groups with matching clinical characteristics was 72% (76/106 patient visits). A trend for greater prevalence of HDV RNA was noted at initial presentation in homosexuals (82%) compared to intravenous drug abusers (60%, P less than 0.05) and this trend appeared to be maintained during two years of sequential follow-up. The seroprevalence of co-appearing IgM and IgG anti-HD antibodies was similar in the two groups of patients. However, in HDV RNA positive homosexuals IgG anti-HD antibody was more prevalent, and additionally, assumed concordance with HDV RNA of 92% although the significance of this observation is unclear. The difference in prevalence of HIV in the two groups did not reach statistical significance. Prospective studies are required to confirm differences in HDV replication in various patient groups and to define underlying mechanisms.     

Development of a hepatitis delta virus antibody assay for study of the prevalence of HDV among individuals infected with hepatitis B virus in China

Co-infection with hepatitis delta virus (HDV) and hepatitis B virus (HBV) has been shown to be associated with a more severe form of acute and chronic hepatitis. Cloning and expression of recombinant HDV antigen (rHDAg) in Escherichiacoli are described. Using purified rHDAg, a cost-effective indirect anti-HDV enzyme-linked immunosorbent assay (ELISA) kit was developed. Direct comparison of 15 known HDV-positive sera and 15 HDV-negative sera showed concordance agreement between the new assay kit and the Abbott Murex Anti-Delta (total) kit. In addition, 1,486 hepatitis B surface antigen (HBsAg) positive blood samples collected from various areas of China were tested using this indirect anti-HDV ELISA. It was found that 1.2% (95% CI: 0.7-1.9%) of the samples were anti-HDAg positive. It is suggested that the prevalence of HDV and HBV co-infection in China is relatively low.     

Prevalence of hepatitis B, C, and delta virus infections among children in Mongolia: progress in childhood immunization

Mongolia is highly endemic for hepatitis B virus (HBV), hepatitis C virus (HCV), and hepatitis delta virus (HDV) infections among apparently healthy adults. However, the age-specific prevalence of ongoing HBV, HCV, and HDV infections among children in Mongolia remains unknown. Therefore, samples obtained from a total of 655 apparently healthy children of 0.3-15 years of age (307 boys and 348 girls; age, mean +/- standard deviation [SD], 8.4 +/- 4.2 years) living in Mongolia, between October 2005 and January 2006, were tested for serological and molecular markers of HBV, HCV, and HDV infections. Although 88.7% of the 655 children studied were immunized against hepatitis B, 64 (9.8%) tested positive for hepatitis B surface antigen (HBsAg) and/or HBV DNA and 13 (2.0%) for HDV RNA. Twenty-seven children (4.1%) had detectable HCV RNA. Collectively, 82 (12.5%) were viremic for one or more of these viruses, including eight children with dual viremia of HBV/HCV and one child with triple HBV/HCV/HDV viremia. When children without anti-HBc, anti-HCV and anti-HDV IgG (n = 510) served as a control, a history of hospitalization was significantly associated with HBV viremia (P < 0.0001), anti-HBc positivity (P < 0.0001), and HCV viremia (P = 0.0001). HBsAg mutation was found in 18 (31.6%) of the 57 children with viremia, including those at amino acid position 126, 127, 129, 131, 134, 143 or 144. There were no significant differences in the frequency of HBsAg mutation in relation to age, sex, and hepatitis B vaccination status of the children, suggesting that HBsAg mutation plays a limited role in failure of vaccination in Mongolia.     

Seroepidemiology of hepatitis A, B, and D viruses and human T-lymphocyte tropic viruses in Japanese drug abusers

To evaluate the prevalence of hepatitis virus markers and human T-cell lymphotropic virus infections among drug abusers in Japan, serum samples were collected from 91 male drug abusers at the Shinshu University Hospital and the rehabilitation facility in Matsumoto and from 519 healthy male blood donors as controls. Sera were tested for antibody to hepatitis A virus (anti-HAV), hepatitis B surface antigen (HBsAg), antibody to HBsAg (anti-HBs), antibody to hepatitis B core antigen (anti-HBc), immunoglobulin M anti-HBc (IgM anti-HBc), antibody to hepatitis D virus (anti-HDV), antibody to HTLV type 1 (anti-HTLV 1), and antibody to human immunodeficiency virus (anti-HIV). The prevalence of anti-HAV was 13.2% in drug abusers and 10.8% in controls (not significant). The prevalences of HBsAg, anti-HBs, anti-HBc and exposure rate to hepatitis B virus (HBV) were 4.4%, 24.2%, 31.9%, and 35.2%, respectively, in drug abusers and 0.8%, 6.7%, 9.6%, and 9.6% in controls. The exposure rate to HBV was significantly different (P less than 0.001). IgM anti-HBc and anti-HDV were not detected in any sera. Anti-HTLV I was detected in three drug abusers (3.3%) and in one (0.2%) of the controls (P less than 0.01). All sera were negative for anti-HIV in all subjects. Infection with HBV and HTLV I is more common among drug abusers than in the general population of blood donors in Japan.     

Fulminant hepatitis in asymptomatic hepatitis B surface antigen carriers in Greece

Eleven male fulminant hepatitis (FH) patients (mean age: 47.7 +/- 16 years) positive for hepatitis B surface antigen (HBsAg) but negative for IgM antibody to hepatitis B core antigen (IgM anti-HBc) were admitted consecutively to the Athens Hospital for Infectious Diseases between May 1981 and November 1983. Because of the absence of IgM anti-HBc, determined by an enzyme immunoassay, these patients were considered to be HBsAg carriers with a superimposed acute hepatitis. Three of the 11 patients received immunosuppressive chemotherapy during the six months before the onset of the acute hepatitis. None of the patients was homosexual or a drug addict. Infection with hepatitis A virus (HAV), hepatitis B virus (HBV), or hepatitis delta virus (HDV) was detected with serologic markers and/or molecular hybridization techniques. Fulminant hepatitis was attributed to spontaneous reactivation of chronic hepatitis B in four patients, chemotherapy-induced reactivation of chronic hepatitis B in three patients, HDV superinfection in one patient and possible superinfection by non-A, non-B agent(s), HDV, or HDV-like agents in three patients. Reactivation of chronic hepatitis B was an important cause of apparent acute hepatitis in heterosexual male HBsAg carriers from an area with a high prevalence of HBV infection.     

Seroepidemiological studies on hepatitis B and D viruses infection among five ethnic groups in southern Taiwan

In order to compare the prevalence of hepatitis B virus (HBV) and hepatitis D virus (HDV) infection among five ethnic groups in Pingtung County of southern Taiwan, a total of 240 serum samples were collected from September to October, 1985, from the following five ethnic groups: Taiwanese, Hakka, Mainland Chinese, aboriginal Paiwanese, and aboriginal Rukaiese. Ages of subjects ranged from 5 to 69 years. All sera were tested for hepatitis B surface antigen (HBsAg), surface antibody (anti-HBs), and core antibody (anti-HBc) by radioimmunoassay (RIA). Hepatitis B e antigen (HBeAg) and antibody to hepatitis D antigen (anti-HDV) were also tested for those with HBsAg-positive sera. Results showed that 44.1% of all sera examined were negative for HBsAG but positive for both anti-HBs and anti-HBc; additionally, 24.6% were negative for both HBsAg and anti-HBs but positive for anti-HBc. Only 134 serum samples showed negative results for HBV markers, indicating an HBV infection rate of 88.8%. The anti-HDV positive rate was estimated to be 2.7% among HBsAg-positive subjects. The HBsAg-positive rates among Rukaiese, Paiwanese, Hakka, Taiwanese, and Mainland Chinese were 25.8, 22.5, 16.7, 12.9, and 10.0%, respectively; while the prevalence rates of HBV infection among the above five groups were 94.2, 94.6, 85.4, 87.5, and 82.5%, respectively. Differences in the HBsAg-positive rate and HBV infection rate among these ethnic groups were statistically significant. We conclude that people living in Pingtung County are more frequently infected with HBV when compared with inhabitants in northern Taiwan.     

成年树鼩实验感染丁型肝炎病毒的初步研究

在证实成年树可感染人乙型肝炎病毒（ＨＢＶ）的基础上，进行了丁型肝炎病毒－乙型肝炎病毒（ＨＤＶ／ＨＢＶ）实验感染的探索。ＨＤＶ／ＨＢＶ阳性人血清经同时和重叠感染方式接种于成年树后，定期留取感染树血清及肝组织，检测血清中ＨＢｓＡｇ、ＨＤＡｇ、抗－ＨＤ、ＨＢＶＤＮＡ及ＨＤＶＲＮＡ，初步探讨成年树实验感染ＨＤＶ的可能性。研究发现：①成年树对人ＨＢＶ易感，ＨＢｓＡｇ阳性率为７５％，其血清学反应及肝组织病理改变与文献报道一致；②ＨＤＶ可通过同时和重叠两种方式感染成年树，感染树血清中可出现ＨＤＡｇ及抗－ＨＤ，经分子杂交证实其血清及肝内均有ＨＤＶＲＮＡ和ＨＢＶＤＮＡ存在，且可导致明显的肝细胞损伤。结果提示：成年树既可感染人ＨＢＶ也可感染ＨＤＶ，可作为研究ＨＤＶ人工感染的实验动物；成年树感染ＨＤＶ后的特点与人及黑猩猩感染时十分相似，能较好地反映人丁型肝炎的真实情况。     

Persistent delta antigenaemia in chronic delta hepatitis and its relation with human immunodeficiency virus infection.

The prevalence of persistent hepatitis delta (HD) antigenaemia and associated factors in patients with chronic infection with the hepatitis delta virus (HDV) were investigated. Among 157 consecutive patients known to be carriers of hepatitis B surface antigen (HBsAg), 36 (23%) had one serum marker of HDV infection (anti-HD and/or HDAg). Nine of the patients with an HDV marker were HDAg positive, including three who were anti-HD negative. A follow-up over a mean period of 13 months showed that five of five patients had a persistent HD antigenaemia. This serological profile was associated with the presence of antibody to the human immunodeficiency virus (anti-HIV) (P < 0.01), serum HIV antigen (HIVAg) (P < 0.2), and the female sex (P < 0.05). Persistent HD antigenaemia could be the consequence of the suppression of T cell cytotoxic activity against hepatocytes expressing HDAg, a lower humoral response, and/or hormonal factors.     

Prevalence of antibody to delta antigen among HBV carriers in Japan

Of 280 hepatitis B virus (HBV) carriers in Kure, Hiroshima Prefecture, Japan, 14 (5.0%) were seropositive for antibody to delta antigen (anti-HD by radioimmunoassay. HBV carriers with chronic liver disease had a greater frequency of seropositivity of anti-HD than asymptomatic HBV carriers (7% vs. 0%, P less than 0.05). Among the various geographic regions of Kure, the east suburban area had a significantly higher prevalence of anti-HD when compared with all other regions combined (9.8% vs. 2.7%, P less than 0.025). It is suggested that hepatitis delta virus (HDV) infection exists in Japan and HDV may be an etiologic agent of chronic liver disease.     

The serology of delta hepatitis and the detection of IgM anti-HD by EIA using serum derived delta antigen

A sensitive and specific capture assay for IgM antibody to hepatitis D virus (HDV) was developed employing serum-derived delta antigen (HDAg). In a retrospective and prospective study of an outbreak of hepatitis B (HB), 135 hepatitis B surface antigen (HBsAg) positive drug-abusers with acute hepatitis and 18 HBsAg carriers, attending various hospitals and clinics in Dublin, were found to be infected with HDV. Serological follow-up was available from 24 of those with acute hepatitis allowing a comparison of the duration and level of IgM anti-HD with the more commonly used markers, HDAg and anti-delta (anti-HD), and an assessment of the usefulness of each. HDV and HB serology was grossly altered by human immunodeficiency virus (HIV) in two patients, with severe clinical manifestation in one. All 135 patients with HDV co-infection had delta antigenaemia. In co-infections with optimum sampling times, the mean duration of delta antigenaemia was 21 days. IgM anti-HD was always found between HDAg and sero-conversion to anti-delta and was the only 'window' marker present in five cases. The mean duration of IgM anti-HD was four weeks (optimum at 2.8 weeks) and was of moderate or low titre and occurred simultaneously with HDAg in 78%. In HDV-infected HBsAg carriers, high-titre IgM anti-HD (greater than 1/10,000) persisted for the duration of the study and is a useful indicator of chronic HDV infection. IgM anti-HD was not found in 202 random blood donors nor in 205 patients with non-B hepatitis or other disorders.(ABSTRACT TRUNCATED AT 250 WORDS)