The impact of vaccination and antiviral therapy on hepatitis B and hepatitis D epidemiology

The major cause of liver cancer around the globe is hepatitis B virus (HBV), which also contributes to a large number of deaths due to liver failure alone. Hepatitis delta virus (HDV) is as potentially alarming as HBV since life threatening cases are 10 times more likely with HBV-HDV dual infection compared to HBV monoinfection. So far, there is no established effective treatment against HDV and the only preventive action suggested by the World Health Organization is to introduce HBV vaccination for children immediately after birth (newborns) and thus reduce the available pool for HDV infection. Here the main objective is to understand the complex dynamics of HBV-HDV infection in a human population that can inform public health policy makers on the level of different preventive measures required to eliminate HBV and HDV infections. Model simulations suggest that HBV vertical transmission and HBV vaccination rates for newborns are instrumental in determining HBV and HDV prevalence. A decrease in HBV prevalence is observed as vaccination coverage increases and it is possible to eradicate both HBV and HDV using high vaccination coverage of ≥80% in the long term. We further found that HDV presence results in lower HBV prevalence. An application of our model to China revealed that vaccinating every newborn in China will further prevent 1.69 million new infections by 2028 as compared to the current 90% vaccination coverage. Although, higher vaccination coverage of newborns should eliminate both HBV and HDV over a long time period, any short term strategy to eradicate HDV must include additional preventive measures such as HBV adult vaccination. Implementation of HBV adult vaccination programs at a rate of 10% per year over 15 years will further prevent 39 thousand new HDV infections in China by 2028 as compared to HBV vaccination programs solely for newborns.

Epidemiology of acute and chronic hepatitis B and delta over the last 5 decades in Italy

The spread of hepatitis B virus (HBV) infection has gradually decreased in Italy in the last 5 decades as shown by the steady reduction in the incidence rates of acute hepatitis B, from 10/100000 inhabitants in 1984 to 0.85/100000 in 2012, and by the reduced prevalence of hepatitis B surface antigen (HBsAg)-positive cases among chronic hepatitis patients with different etiologies, from 60% in 1975 to about 10% in 2001. The prevalence of HBsAg chronic carriers in the general population also decreased from nearly 3% in the 1980s to 1% in 2010. Linked to HBV by its characteristics of defective virus, the hepatitis delta virus (HDV) has shown a similar epidemiological impact on the Italian population over time. The incidence of acute HDV infection decreased from 3.2/100000 inhabitants in 1987 to 0.8/100000 in 2010 and the prevalence of HDV infection in HBsAg chronic carriers decreased from 24% in 1990 to 8.5% in 2006. Before the beneficial effects of HBV mass vaccination introduced in 1991, the decreased endemicity of HBV and HDV infection in Italy paralleled the improvement in screening blood donations, the higher standard of living and impressive reduction in the birth rate associated with a marked reduction in the family size. A further contribution to the decline in HBV and HDV infections most probably came from the media campaigns to prevent the spread of human immunodeficiency virus infection by focusing the attention of the general population on the same routes of transmission of viral infections such as unsafe sexual intercourse and parenteral exposures of different kinds.

Hepatitis delta virus: the molecular basis of laboratory diagnosis

Infection with hepatitis delta virus (HDV), a satellite virus of hepatitis B virus (HBV), is associated with severe and sometimes fulminant hepatitis. The traditional methods for the diagnosis of HDV infection, such as detection of serum anti-HD antibodies, are sufficient for the clinical diagnosis of delta infection. However, such techniques lack the sensitivity and specificity required to more accurately characterize the nature of HDV infection and to assess the efficacy of therapies. Recent improvements in molecular techniques, such as HDV RNA hybridization and RT-PCR, have provided increased diagnostic precision and a more thorough understanding of the natural course of HDV infection. These advances have enhanced the clinician's ability to accurately evaluate the stage of HDV infection, response to therapy, and occurrence of reinfection after orthotopic liver transplant. This review focuses on the recent advances in the understanding of the molecular biology of HDV and in the laboratory diagnosis of HDV infection.

Injecting behaviours and prevalence of hepatitis B, C and D markers in New Zealand injecting drug user populations

AIM

To determine the seroprevalence of hepatitis C virus (HCV), hepatitis B virus (HBV) & hepatitis D virus (HDV) markers of infection among injecting drug user populations in New Zealand and to examine the relationship between demographic features, risk behaviours and infection.

METHODS

A total of 323 current injecting drug users completed a questionnaire that explored their needle and syringe using behaviours. Information was collected on injection pattern, sharing behaviours and methods of cleaning needles and syringes. Two hundred and forty-one respondents gave blood samples which were tested for hepatitis B, C and D markers.

RESULTS

Over half the respondents (59%) were male and 41% were female. Most (89%) identified as European. Sixty-four percent were anti-HCV positive. The likelihood of infection increased with age and duration of injecting. Forty-one percent (33/81) of those aged 25 or under, sixty-four percent (45/70) of those aged 26-30 and eighty-seven percent (78/90) over 30 were anti-HCV positive. Those who tested anti-HCV positive had been injecting for an average of 12.0 years compared to 6.0 years for those were anti-HCV negative. The results for hepatitis B are to be reported fully at a later date. Sharing behaviour was also a factor although this was less important as an independent factor. Comparisons with earlier surveys suggested that there has not been a significant decline in the rate of sharing needles and syringes since the initial period following introduction of the needle exchange programme.

CONCLUSION

The prevalence of hepatitis C infection is common among injecting drug users of all ages. Without a significant reduction in sharing behaviour, particularly among younger injecting drug users, it is unlikely that the prevalence of hepatitis C among injecting drug users will decline in the future. Evidence suggests that the carriage of hepatitis C is higher than that of hepatitis B which would help explain the differing rates of prevalence. However, the risk of future transmission of other parenterally transmitted diseases remains high without a further significant decline in sharing behaviour.

Chronic viral hepatitis

Among hepatitis A to E viruses, hepatitis B, C, and D viruses can cause chronic hepatitis, in both children and adults. Hepatitis B virus (HBV) infection is the most prevalent and important one. Perinatal transmission accounts for about 40-45% of chronic HBV infection in hyperendemic areas. Horizontal transmission through intramuscular injection using non-sterile needles and intrafamilial spread accounts for the other half of carriers. During the natural course of HBV infection, the host gradually clears HBV and hepatitis B e antigen (HBeAg), liver damage and elevation of aminotransferases occur during the process of HBV clearance. The most effective way to eliminate HBV infection is immunoprophylaxis starting since birth. It can prevent both HBV and hepatitis D virus (HDV) infections. Hepatitis C virus (HCV) infection in children occurs mainly in high risk children, such as those who received blood product or injection using non-sterile needles, or infants of HCV viremic mothers, etc. Screening of blood product reduced markedly the prevalence of post-transfusion HCV infection, but the prevention of sporadic cases requires HCV vaccination which is still under investigation.