The CDC announced Friday that a Maryland who man recently died of rabies, contracted the disease from a kidney transplant over a year ago.
The man who died in Maryland and the three other people -- in Florida, Georgia and Illinois -- received organs from a person who died in Florida in 2011.
Doctors knew the donor had encephalitis, an inflammation of the brain, when they harvested the organs. However, they didn't know rabies was the cause. Since rabies wasn't suspected, no test for rabies was done before the organs were donated.
After becoming ill, the Maryland man who received an infected kidney died February 27. Health officials investigating his death made the rabies diagnosis in March. Officials then re-examined the donor's death and determined the donor also died of rabies, according to the CDC.
Now all family members and health care workers who might have had close contact with the donor or the recipients need to be examined for rabies.
This isn't the first time this has happened in the U.S. Four people died when infected organs and tissue were taken from a donor with rabies. No one knew the donor had rabies until after the recipients became ill.
Organ donors are not routinely tested for rabies, even if they show the signs. One reason is rabies is extremely rare, with only one to three cases a year nationwide, according to the CDC's Dr. Richard Franka.
After extensive testing the CDC determined that both donor and recipient died from the raccoon-type rabies virus.
The other three recipients were immediately contacted. They show no signs of rabies but are getting anti-rabies treatment.