Acute - Of short and sharp course; not chronic (new infection).

ALT (alanine aminotransferase) - An enzyme normally produced by the liver; blood levels may increase in cases of liver damage; formerly known as SGPT.

Anti-HAV - Antibody to hepatitis A virus.

Anti-HAV IgM - M class immunoglobulin antibody to hepatitis A virus.

Anti-HBc - Antibody to hepatitis B core antigen.

Anti-HBc IgM - M class immunoglobulin antibody to hepatitis B core antigen.

Anti-HBe - Antibody to hepatitis B e antigen.

Anti-HBs - Antibody to hepatitis B surface antigen.

Antibody (Ab) - A Y-shaped protein molecule (immunoglobulin) in serum or body fluid that either neutralizes an antigen or tags it for attack by other cells or chemicals; acts by uniting with and firmly binding to an antigen. The prefix anti-followed by initials of a virus, refers to a specific antibody against the virus.

Antigen (Ag) - A substance capable of causing the body to produce specific antibodies; any substance that stimulates lymphocytes (white blood cells) to initiate an immune response.

Assay - A test to determine the presence, absence or quantity of one or more components of a substance.

Asymptomatic - Without overt symptoms.

Calicivirus - A family of small RNA viruses, HEV is a member of the calicivirus family.

Chronic hepatitis - A condition in which liver inflammation persists for more than six months.

Chronic infection - An individual with HBsAg in the serum for periods longer than six months is infectious, and may or may not exhibit symptoms of hepatitis; also applies to a large number of individuals with HCV infection.

Chronicity - The quality of being chronic or persisting over a long period of time.

Cirrhosis - Irreversible scarring of the liver that may occur with chronic hepatitis.

Coinfection - A condition whereby an uninfected individual becomes infected with two or more different infectious agents.

Core - The central part of the hepatitis B virus, as well as other viruses.

Delta agent - Previously used name to identify a unique RNA virus that causes acute or chronic hepatitis; requires hepatitis B virus for replication and only infects patients who are HBsAg positive; comprised of delta antigen core and hepatitis B surface antigen coat; today referred to as hepatitis D virus (HDV).

DNA (deoxyribonucleic acid) - The coded genetic material in the nucleus of most cells that controls heredity; automatically controls the formation of RNA, which spreads throughout the cell and controls the formation of specific proteins. The genome of HBV is DNA.

DNA polymerase - An enzyme that catalyzes DNA synthesis; present in the core hepatitis B virus.

Endemic - Present in a community at all times.

Enteric - Pertaining to the intestines.

Enteric route - The spread of organisms via the fecal/oral cycle of infection.

Enterovirus - One of a group of similar viruses infecting the gastrointestinal tract and discharged in the feces.

Epidemiology - The study of the incidence, distribution and control of disease in a population.

Flavivirus - A family of small RNA viruses, formerly referred to as the arboviruses. HCV is a member of the flavivirus family.

Fulminant hepatitis - The most severe form of hepatitis; may lead to acute liver failure and death.