• hepatitis D
• epidemiology

Hepatotropic viruses can infect hepatocytes causing a host defence reaction and subsequently scaring of the liver—if the infection is not cleared. The threats of chronic viral hepatitis partially vanished due to the revolution of antiviral treatment options first for hepatitis B and more recently for hepatitis C. Persistent HCV infection can nowadays be cleared with direct acting antiviral agents leading to impressive improvements in the clinical long-term outcome with reduced incidences of hepatic decompensation and hepatocellular carcinoma. Similarly, durable suppression of HBV replication has been shown to prevent disease progression and even to normalise life expectancy unless hepatocellular carcinoma appears.1 Unfortunately, the scenario is completely different for hepatitis D virus (HDV) infection. Coinfection of HBsAg-positive individuals with HDV causes the most severe form of chronic viral hepatitis with earlier development of liver cirrhosis, higher incidence of hepatocellular carcinoma and increased liver-related and overall mortality.2 3 In addition, treatment options for hepatitis D are currently limited. Pegylated interferon alpha has been shown to suppress HDV replication in about 25% of patients but only a minority of patients can be treated with interferon-based therapies and late relapses after initial viral control occur frequently.4 Still, the extent of the global disease burden caused by HDV infection is a matter of debate. The WHO Global Hepatitis Report 2017 highlighted the issue of uncertainty regarding the HDV burden.5 While both the European Medicines Agency and the Food and Drug Administration granted new compounds to treat hepatitis D an orphan drug status (meaning that less than 5 or less than 7.5 out …