IDU: See Injecting Drug User; also IVDU.

IEC: Information, education, communication.

IVDU: See Injection Drug User.

Illicit drugs: Substances that impair judgment.

Immune deficiency: When certain parts of the immune system no longer function, making a person more susceptible to certain diseases.

Immune system: The various cells and proteins that work together to fight infections and regulate many of the body’s functions. First, the immune system identifies an infectious agent (e.g. virus or bacteria) and the antigens that are part of it. It then makes antibodies that are designed to counteract the antigens of the particular infection, which then try to locate and destroy the infection. Normally, once antibodies are created, they remain in a person’s immune system for the remainder of his/her life, preventing the person from falling ill from the same infection more than once.

Immunization: Protection against a particular disease by vaccination (injection).

Immunotherapy: Treatment to stimulate or restore the ability of the immune system to fight infection and disease. Also used to lessen side effects that may be caused by some cancer treatments.

Impact mitigation: Programmes to assist families and communities to cope with the physical and psycho-social effects of an illness, to develop and take individual and collective responsibility for alternative livelihoods when there is a loss of income, to deal with stigma, and to support orphaned children for whom care is needed.

Incubation period: The period of time between the entry of an infecting pathogen (such as HIV) into the body, and the first symptoms of the disease.

Injection Drug User (IDU or IVDU): A term used to refer to people who inject drugs directly into their bloodstream by using a needle and syringe. Also referred to as injecting drug user.

Integration: The process by which HIV reproduces in white blood cells.

Intercourse: Sexual activity that involves penetration of the vagina and anus or oral genital contact.

Intra-: Prefix (first part of a word) which means within or into.

Intravenous: Within or into the veins. Intravenous drugs are injected directly into the veins.