Malaria can indeed be transmitted by transfusion of packed red blood
cells, but is an uncommon event. Donor screening for recent history
of travel to malaria endemic regions weeds out people who may have
been infected. Malaria does not cause asymptomatic infection, so
infected individuals are usually sick and are not donor candidiates.
The use of quinine and its derivatives is a cause for deferring blood
donations for at least 6 months, since these drugs can result in the
inhibition of replication of the parasite, but not its death.