What is hepatitis D?

Hepatitis D is a viral inflammation of the liver caused by the hepatitis D virus (HDV). Its key feature is that the hepatitis D virus cannot replicate on its own — to do so, it must have the presence of thehepatitis B virus.

This means that hepatitis D cannot occur without hepatitis B. Infection is only possible in people who already have hepatitis B, or in the event of simultaneous infection with both viruses.

Co-infection with hepatitis B and D is considered to be the most severe form of chronic viral hepatitis. It is characterised by:

• more rapid liver damage;
• a higher risk of developing cirrhosis;
• an increased risk of hepatocellular carcinoma (liver cancer);
• higher mortality rates associated with liver disease.

According to current estimates, the hepatitis D virus affects around 5% of people worldwide who are living with chronic hepatitis B — that is approximately 12 million people. It is believed that hepatitis D co-infection may account for approximately one in five cases of severe liver damage and liver cancer among people with hepatitis B. Important to know: vaccination against hepatitis B is the only effective way to prevent hepatitis D, as the hepatitis D virus cannot survive without the hepatitis B virus.

Prevalence

According to current estimates, around 12 million people worldwide are infected with the hepatitis D virus. At the same time, the results of individual international studies and meta-analyses suggest that the actual prevalence may be significantly higher due to limited testing and underestimation of the incidence in many regions of the world. On a global scale an estimated 5% of people with hepatitis B also have hepatitis D. It is this co-infection that largely determines the severity of the disease.

The situation in Ukraine

According to data from the Public Health Centre of the Ministry of Health of Ukraine dated 18 March 2026, among those tested who were HBsAg-positive :

• The prevalence of antibodies to the virus of hepatitis D is approximately 7.5%;

• In the general population, the prevalenceof antibodies to HDVis approximately0.06%,which is comparable to the European level(≈0.05%).

At the same time, according to available data, only 126 people diagnosed with hepatitis D sought medical help.

In view of this, it can be tentatively estimated that 5–7.5% of people with hepatitis B in Ukraine may have a hepatitis D co-infection.

 In this case the estimated number of people with HDV in Ukraine could be around 27,967.

This indicates significant underdiagnosis of the disease and highlights the need for routine testing for hepatitis D among HBsAg-positive patients.

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