A Maryland man who died of rabies was infected by a kidney transplant he received more than a year ago, not by an animal bite.
According to BBC News, three other patients who were given transplanted organs from the same donor are now being treated.
The Centers for Disease Control (CDC) said doctors never suspected the donor died of rabies and did not test for it. There are usually no more than three cases of rabies diagnosed in the US each year.
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"The organ transplantation occurred more than a year before the recipient developed symptoms and died of rabies," the CDC told BBC, adding that such a long incubation period is usual but not unheard of.
The donor, who died of raccoon rabies in Florida in 2011 after moving from North Carolina, had its kidneys, heart and liver sent to recipients in Florida, Georgia, Illinois and Maryland, reported CBS News. Tissue sample tests from the donor confirmed that the rabies transmission was caused by organ transplantation.
An investigation by the Maryland Department of Health and Mental Hygiene was launched in early March after the recipient died, according to Fox News. The results showed that the man had no exposure to the usual source of rabies transmission, which is exposure to animals.