On 13 September 1989 "Donor Y" received a unit of plasma from the BTSB which was almost certainly contaminated with hepatitis C. (Check back tests of her plasma donations after this date tested positive for hepatitis C, a sub-type different from the one that infected Patient X.) With the emergence of HIV in the 1980s and the BTSB's previous difficulties with hepatitis contamination, the BTSB now had a precautionary protocol surrounding plasma donations by mothers undergoing exchange transfusions: Plasma donations from such women could not be included in the production of blood products until they had given birth and had a blood test showing they were clear of HIV, hepatitis B and hepatitis C.
