A man in the US state of Maryland has died of rabies, which he contracted from an infected kidney transplant more than a year ago, health officials say.
The early March death has led officials to treat three other patients who received organs from the same donor.
The Centers for Disease Control (CDC) say doctors did not suspect rabies as the cause of death in the donor and did not test for it.
Typically no more than three cases of rabies are diagnosed in the US yearly.
The donor died of raccoon rabies in Florida in 2011 after moving there from North Carolina.
The recipients of the donor's heart, liver and other kidney are receiving anti-rabies vaccines, the CDC said in a news release on Friday. They live in Illinois, Georgia and Florida.
"The organ transplantation occurred more than a year before the recipient developed symptoms and died of rabies," the CDC said, adding such an incubation period is much longer than usual but not unheard of.
Despite this case, the benefits of organ transplantation "generally outweigh the risks", the CDC said in a statement.