Can’t they test the blood before passing it on?
There is no available test that completely removes the 'window period' where someone has HIV in their blood which won’t show up in tests. It is true that 'fourth generation' or RNA testing, which has been the standard test since 2007, can give a quicker result than before, but whether the window period lasts for one week or 12 weeks, it still exists and still presents a risk. However, changes in science and technology are part of what the review has taken into account.
Not all blood products can be heat-treated to kill off viruses that they may contain. It is also important to remember that blood is still pooled and one donation is usually shared among several recipients. It should also be remembered that the recipients are unlikely to know that they are at risk until after they have potentially infected others.
The Blood Service freely admits that no test is 100 per cent perfect and that mistakes, however rare, can be made in the laboratory. Taking blood from populations who are at a low risk of having HIV reduces the number of infected donations that could be missed by testing which is why selection takes place before donations are given. Since 2003, there have been no new HIV diagnoses resulting from UK blood donations (Aidsmap).