The revelation last month that a man was infected with HIV through a tainted blood product was another reminder that people at risk should not donate blood.

Part of the problem is that some people persist in trying to use the donation process as a way to be tested for HIV.

Unfortunately, it is technically impossible to completely exclude tainted blood, and plasma contaminated with the human immunodeficiency virus is liable to slip through safety checks at donation centers if the donor is in the initial phase of infection.