Updated

A Maryland patient who underwent an organ transplant has recently died of rabies, which he reportedly caught through the transplanted organ, according to the Centers for Disease Control and Prevention and Maryland Department of Health and Mental Hygiene.

The patient was one of four people who received an organ from one particular donor. The CDC said it tested tissue samples from the donor and the dead recipient in order to confirm the connection.

Currently, the CDC is testing the three other recipients who received organs from this donor, and as a precaution, they will receive anti-rabies shots.

The Maryland Department of Health and Mental Hygiene began its investigation in early March after the organ recipient died. The agency found the person had no exposure to animals, which is the usual source of rabies transmission to humans.

Transmission through organ transplants is very rare.

The patient developed symptoms about one year after the transplant, which is longer than the usual rabies incubation period of one to three months. However, there have been cases of longer incubation periods.

The CDC said the patient and the donor tested for the same type of rabies virus, which was linked to a raccoon. Only one other person in the U.S. has reportedly died from a raccoon-type rabies virus, the CDC said.

The donor’s organs went to four people in Florida, Georgia, Illinois and Maryland in 2011. While he was living in Florida during his illness and death, he had previously been a resident of North Carolina, where it is believed he was exposed to the rabies virus. The CDC is working with health care facilities in all five states to identify people who may have been in close contact with the initial donor or the organ recipients, as they may need treatment too.

The CDC said all potential organ donors in the U.S. are screened and tested to make sure they do not pose a risk for infectious diseases.

There are usually one to three human rabies cases in the U.S. each year, according to the agency.  Rabies is not usually tested in organ transplant donors because it is so rare, and it is difficult to confirm results in the short time doctors have to keep organs viable.

Rabies infects the central nervous system and can cause disease in the brain, which can lead to death within just a few days. The most rabid animals in the U.S. include raccoons, skunks, foxes and bats.