ABC and D?

By Peter Galvin, MD

Most people have heard of hepatitis viruses A, B, and C, but did you know there is a hepatitis D virus (HDV) as well? Hepatitis D is an incomplete virus, however. Viruses are made up of genetic material that is surrounded by a wall that protects the genetic material from the environment (see photo). But HDV is incomplete because it lacks a wall, thereby requiring it to exist within a host virus. This host virus is hepatitis B (HBV). HDV can only infect human cells in the presence of HBV. Therefore, people with HDV infection always have a simultaneous HBV infection. HDV can be acquired as a coinfection with HBV or as a superinfection if they already have chronic HBV infection.

HDV affects approximately 12 to 72 million people worldwide. HDV, like HBV and HCV, is spread through contact with the blood or bodily fluids of an infected person. Those at the highest risk of HDV infection include IV drug users, sex workers, men who have sex with men, patients undergoing hemodialysis, those with HIV infection, and immigrants from areas of the world that have high levels of HDV infection. About 95% of those with acute HBV/HDV infection clear their infections spontaneously after a brief illness. However, more than 90% of those with active HBV infection who subsequently acquire HDV infection develop chronic infection that lasts more than six months. Chronic HBV/HDV infection causes a more rapid progression to cirrhosis, liver disease, and liver disease-related death than chronic HBV infection alone. More than 50% of those with chronic HDV infection will die within 10 years of diagnosis.

A blood test can detect the presence of HDV antibody, which indicates a current or past infection. If the antibody test is positive, a polymerase chain reaction (PCR) test detects the level of virus in the blood and is used to diagnose a current HDV infection and determine viral blood levels and response to treatment. There are currently no FDA-approved treatments specifically for HDV, however because HDV needs the presence of HBV to exist, the treatment goal for HDV is to eliminate HBV infection. Most people will recover from acute HBV infection without treatment, although for those (usually immunocompromised) people who develop chronic HBV infection there are numerous, successful treatments, most of which involve anti-viral medications. Liver transplant is usually required for those with advanced liver disease from chronic HBV/HDV infection.

There is no vaccine for HDV, however vaccination for HBV infection for those without prior HBV infection will prevent HDV infection. The HBV vaccine and hepatitis B immunoglobulin (antibody) given at birth to infants born to HBV/HDV-infected mothers can prevent HBV and HDV transmission. The HBV vaccine is also recommended for sexual and household contacts of people with HDV infection who have not previously received the HBV vaccine and have not had prior HBV infection. For those with chronic HBV infection, the only preventative measure for HDV infection is avoiding contact with blood and bodily fluids of those with HDV infection.

For more information go to the website of the National Institute of Diabetes and Digestive and Kidney Diseases at www.niddk.nih.gov