Risky sexual behavior is the sole independent predictor of acute HDV.
Hepatitis B virus (HBV) vaccination is contributing to a precipitous drop in acute Delta virus hepatitis (HDV) in Italy over the last 3 decades, potentially because of a public health campaign.
A team, led by Tommaso Stroffolini, Department of Tropical and Infectious Diseases, Policlinico Umberto I, evaluated incidence of and risk factors associated with acute Delta virus hepatitis in Italy following the introduction of the compulsory vaccination against hepatitis B virus in 1991.
HDV is a defective, single stranded RNA virus that requires hepatitis B surface antigen (HBsAg) envelop for assembly and transmission. The virus was first discovered in Italy in 1977. Infections can occur simultaneously with hepatitis B virus infections or in chronic carriers of HBsAg. While the hepatitis B vaccine protects against de-novo infections with both viruses, it does not protect chronic HBV carries against superinfections with hepatitis delta virus.
There remains a lack of data-based guidance worldwide on acute Delta virus hepatitis.
In the study, the investigators obtained data from the National Surveillance System of acute viral hepatitis (SEIEVA), an enhanced surveillance system coordinated by the Italian National Institute of Health that was established in 1985.
The data was assessed of independent predictors using logistic-regression analysis.
The overall incidence of acute HDV per 1 million inhabitants declined between 1987 and 2019, from 3.2 cases to 0.04 cases. This was parallel to numbers found in HBV per 100,000 people, which declined from 10.0 to 0.39 in the same time period.
However, the age of the patient population infected by the virus did increase during the course of the study. Between 1991-1999 the median age of a patient was 27 years, while between 2010-2019 the median age of patients was 44 years (P <0.001).
Other trends identified include a decrease in the male to female ratio, which decreased from 3.8 to 2.1, the proportion of coinfections increased from 55-75% (P = 0.003), and HBsAg positive acute hepatitis testing by IgM anti-HDV linearly decreased from 50.1% to 34.1% (P <0.001).
In addition, individuals born overseas accounted for 24.6% of cases between 2004-2010 and 32.1% of cases between 2011-2019.
The investigators also found risky sexual behavior between 2010-2019 was the sole independent predictor of acute HDV (OR, 4.2; 95% CI, 1.4-12.8).
On the other hand intravenous drug use was no longer associated with acute HDV (OR, 1.25; 95% CI, 0.15-10.22).
“In conclusion, HBV vaccination was an effective measure to control acute HDV,” the authors wrote. “Intravenous drug use is no longer an efficient mode of HDV spread. Testing for IgM-anti HDV is a grey area requiring alert. Acute HDV in foreigners should be monitored in the years to come.”
Initial studies show approximately 5% of chronic HBV carriers worldwide are also infect with HDV. However, recent data shows HDV prevalence could be twice as high as previous estimates, while other studies show the prevalence is 4.5% among all HBsAg positive individuals and 16.4% among those attending liver units.