Delta agent is a type of virus called hepatitis D. It causes symptoms only in people who also have a hepatitis B infection.

Hepatitis D virus

Hepatitis D virus (HDV) is  found only in people who carry the hepatitis B virus. HDV may make a recent (acute) hepatitis B infection or an existing long-term (chronic) hepatitis B liver disease worse. It can even cause symptoms in people who carry hepatitis B virus but who never had symptoms.

Hepatitis D infects about 15 million people worldwide. It occurs in a small number of people who carry hepatitis B.

Risk factors include:

• Abusing intravenous (IV) or injection drugs
• Being infected while pregnant (the mother can pass the virus to the baby)
• Carrying the hepatitis B virus
• Men having sexual intercourse with other men
• Receiving many blood transfusions

Hepatitis D may make the symptoms of hepatitis B worse.

Symptoms may include:

• Abdominal pain
• Dark-colored urine
• Fatigue
• Jaundice
• Joint pain
• Loss of appetite
• Nausea
• Vomiting

• Anti-delta agent antibody
• Liver biopsy
• Liver enzymes (blood test)

Many of the medicines used to treat hepatitis B are not helpful for treating hepatitis D. See hepatitis B.

You may receive a medicine called alpha interferon for up to 12 months if you have a long-term HDV infection. A liver transplant for end-stage chronic hepatitis B may be effective.

Persons with an acute HDV infection usually get better over 2 to 3 weeks. Liver enzyme levels return to normal within 16 weeks.

About 10% of those who are infected may develop long-term (chronic) liver inflammation (hepatitis).

• Chronic active hepatitis
• Fulminant hepatitis

Call your health care provider if you have symptoms of hepatitis B.

Prompt diagnosis and treatment of hepatitis B infection can help prevent hepatitis D.

Avoid intravenous drug abuse. If you use IV drugs, avoid sharing needles.

A vaccine is available to prevent hepatitis B. Adults who are at high risk for hepatitis B infection, and all children should get this vaccine.

Perrillo R. Hepatitis B and D. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 78.