The Maryland patient who died of rabies earlier this month contracted the disease from an organ transplant, public health officials announced Friday.
A total of four people received donated organs from a man unknowingly infected with rabies -- leading to the death of one patient more than a year later, according to information provided by the Centers for Disease Control and Prevention and the Maryland Department of Health and Mental Hygiene.
The Maryland man who died had received a kidney, but health officials aren't releasing more information about him for privacy reasons.
Authorities are now scrambling to treat the other three patients -- who received the donor's other kidney, heart and liver -- with getting anti-rabies shots. Those patients live in Florida, Georgia and Illinois.
The donor died at a Florida medical facility in 2011 after moving there from North Carolina.
At the time of the donor's death, rabies wasn't suspected as the cause, so testing for rabies was not performed, the CDC said.
Rabies was only recently confirmed as the donor's cause of death after the current investigation began in Maryland, the agency said.
The organ transplants had occurred more than a year before the Maryland recipient became ill and died -- a period much longer than the typical rabies incubation period of one to three months. There have been other cases of such long incubation periods, however, the CDC said.
The CDC said it's working with public health officials and medical facilities in all five states to identify people who were in close contact with the donor or the four organ recipients. Those people might also need treatment, the agency said.
The Maryland patient's death more than a week ago prompted an investigation by state health officials that led to the announcement Tuesday of the state's first human death from rabies since 1976.
Such deaths are rare, with typically just one to three cases diagnosed per year in the U.S., the CDC said.
The investigation revealed that the Maryland recipient had no reported animal exposures -- which is the usual source of rabies transmission to humans. Investigators then confirmed that both the Maryland recipient and the Florida donor had died from the same type of raccoon rabies virus, the CDC said.
This type of type of rabies virus can infect not only raccoons, but also other wild and domestic animals.
In the United States, only one other person is reported to have died from a raccoon-type rabies virus, the CDC said.