1 Visa - Digits two through six are the bank number, digits seven through 12 or seven through 15 are the account number and digit 13 or 16 is a check digit.  MasterCard - Digits two and three, two through four, two through five or two through six are the bank number (depending on whether digit two is a 1, 2, 3 or other). The digits after the bank number up through digit 15 are the account number, and digit 16 is a check digit.
AIDS is the acronym for acquired immunodeficiency syndrome. 1  It is the stage of HIV infection where a person's immune system is fully compromised, leaving the body open to a wide range of potentially deadly diseases known as opportunistic infections.
HIV (Human Immunodeficiency Virus) Infection - Topic Overview. HIV (human immunodeficiency virus) is a virus that attacks the immune system, the body's natural defense system. Without a strong immune system, the body has trouble fighting off disease. Both the virus and the infection it causes are called HIV. White blood cells are an important part of the immune system. HIV infects and destroys certain white blood cells called CD4+ cells.