VCT: See voluntary counseling and testing.

Vaccine: An injection of a weakened or killed bacteria or virus that is given to protect against later exposure to the same bacteria or virus.

Viral load: The amount of HIV in one millilitre of blood.

Virulence: Aggressiveness, ability to cause disease.

Virus: A sub-cellular organism made up of genetic material and protein that is able to reproduce only within living cells. When a virus infects a cell, it can cause disease, and can even kill the cell itself. Viruses may destabilize the host cell’s normal functions, causing it to behave in a manner determined by the virus.

Voluntary counselling and testing (VCT): The combination of counselling and testing as both a preventive service and a diagnostic tool for HIV infection.