Three hospital patients in Germany appear to have been infected with rabies (search) through organ transplants and are in critical condition, a medical foundation said Wednesday.

Three others who received transplants from the same donor, a woman who died of a heart attack late last year, are doing fine, the German Foundation for Organ Transplants (search) said.

The donor showed no rabies symptoms at the time of her death, although a recent examination of her brain showed typical signs of the disease, the group said. How the woman may have contracted rabies was unclear, but the group noted that she had been in India in October. Although rare in developed countries, rabies kills thousands of people each year in developing nations.

The critically ill patients, hospitalized in the cities of Hanover and Marburg, received the donor's lungs, kidneys and a pancreas. All showed rabies symptoms, the group said. A patient in Heidelberg who received the liver, as well as two patients in Mainz who received her corneas, were in good health.

"Something like this has never happened in Germany," foundation head Guenter Kirste said in a statement. "Unfortunately there is no way to medically rule out such rare infections, despite thorough tests of the donor."

All health professionals who were involved in the transplants or caring for the patients have been identified and inoculated, Kirste said.

Most human cases of rabies arise from dog bites, though many animals can carry the disease. Symptoms include fever, violent spasms, panic, hallucinations and coma leading eventually to death.

Four people in the United States died of rabies last year after receiving infected organs from a donor in Arkansas. That donor had shown no signs of the disease before his death from a brain hemorrhage.