Hepatitis D is an inflammation of the liver caused by the hepatitis D virus. The hepatitis D virus (HDV) is a defective virus, which means that it has no envelope and requires the hepatitis B virus (HBV) to replicate. Hepatitis D therefore only occurs together with hepatitis B. This combination leads to severe chronic courses in the majority of cases.

Hepatitis D occurs worldwide, most commonly in regions with high levels of hepatitis B infection. According to the WHO, geographic hotspots include Mongolia, the Republic of Moldova, and countries in West and Central Africa. Hepatitis D affects five percent of people with hepatitis B worldwide.

Humans represent the pathogen reservoir

Infection with the hepatitis D virus can occur in two ways: Simultaneous infection with HDV and HBV (simultaneous infection) or there is already a chronic hepatitis B infection and there is an additional infection with HDV (superinfection). Like HBV, HDV is transmitted via injured skin (needles, syringes, tattoos, etc.) or via contact with infected blood (e.g. during unprotected sexual intercourse) or blood products.

Simultaneous infection of HBV and HDV can cause mild to severe hepatitis with symptoms indistinguishable from other acute hepatitis illnesses. Typically, after the incubation period, there is fever, fatigue, loss of appetite, nausea, vomiting, dark urine, light-colored stools, and jaundice (icterus, yellow eyes). Patient:s usually recover completely; chronic hepatitis D is rare.

In superinfection, individuals are infected with HDV who already have chronic HBV disease. Superinfection with HDV accelerates the progression of chronic HBV infection to more severe disease in the majority of patients in all age groups. Thus, superinfection can lead to liver cirrhosis a decade earlier than in persons with chronic hepatitis B without HDV infection. Individuals with HDV-induced cirrhosis have an increased risk of developing liver carcinomas.

Pegylated interferon-alpha (INFα) can be used to treat hepatitis D virus infections. To avoid relapses, treatment should last as long as possible; the WHO recommends 48 weeks. Even if the virus does not respond strongly to treatment, drug administration can have a positive effect on the disease. Because severe side effects can occur, the drug should not be given to people with autoimmune disease, psychiatric illness, or advanced cirrhosis.

In July 2020, Hepcludex (active ingredient Bulevirtide) was approved by the EMA (European Medicines Agency) under "Special Conditions" as the first specific active ingredient for the treatment of chronic hepatitis D virus infections. By 2025, the company marketing Hepcludex must collect data on the use of the drug in a patient registry and submit the final results of two ongoing studies.

Vaccination against hepatitis B virus protects against hepatitis D virus infection. In people who are already infected with HBV, the vaccination may not be effective in this regard.

Important measures to protect against infection with HBV and HDV are: protected sexual intercourse, wearing protective gloves when in contact with foreign blood and using syringes only once.

Hepatitis D is a notifiable disease in Austria. Two hepatitis D cases were reported throughout Austria in the first quarter of 2023.

The detection of anti-HCV immunoglobulin G (IgG) and immunoglobulin M (IgM) as well as a detection of HDV RNA in serum allow the diagnosis of a hepatitis D virus infection.

Since the symptoms of the different hepatitis virus types do not differ fundamentally, laboratory diagnosis is essential.

Hepatitis D virus infections are diagnosed by the detection of specific HDV antibodies, as well as HDV RNA in the blood.