The blood was traced to an infected donor, who has also died.

Mr. Anderson declined to disclose the name of the infected donor for reasons of medical confidentiality.

The organs of the infected donor, a man shot to death in a 1985 robbery, were tested for AIDS twice before they were released for transplantation.

This new test identifies infected donors and therefore can reduce the risk of disease transmission through blood transfusion or organ transplantation.

The man, Brian Lykins, 21, died within days of knee surgery from an infection caused by a bacterium that was later traced to an infected donor.

In those early years of the epidemic, before H.I.V. was discovered and a blood test developed, infected donors could not be identified, so blood often contained the virus.

Prior to 1985, many people with hemophilia became infected with the human immunodeficiency virus (HIV) because they received blood products that were contaminated from infected donors.

The centers also try to keep track of donors and their status so that if infected donors return, they can be screened out.

As regards nvCJD, there are indeed concerns that a new and additional risk may be posed by blood and blood products prepared from donations from infected donors.