In the latest news on the subject, experts now believe they can link at least six deaths of organ transplant patients to a rodent virus, which raises questions about whether others may have gone undetected and whether the germ also could spread through blood transfusions.
Although health officials believe the deaths are rare cases, they say a closer study is warranted in view of recent discoveries that have shown that rabies and West Nile virus occasionally spread through donated organs with deadly results.
Dr. Matthew Kuehnert, assistant director of blood safety for the federal Centers for Disease Control and Prevention (CDC), says this is a new phenomenon and a learning experience for those involved. He says they have not previously seen any evidence of transfusion-transmitted infection, but that does not mean it cannot happen.
Earlier this week Rhode Island and Massachusetts officials said they were investigating the deaths of three people who received organs from a female donor whose pet hamster tested positive for lymphocytic choriomeningitis virus, or LCMV. A fourth organ recipient is believed to be recovering.
Health officials in Wisconsin later revealed that four transplant recipients died in the only previously known cases involving the virus in December 2003.
Although the cases were not decisive and the organ donor and a woman who received a lung from him in an operation in Minnesota both tested negative for LCMV, three other transplant patients tested positive for the virus, strongly suggesting the donor was the source.
Epidemiologist for the Wisconsin Department of Health and Family Services, James Kazmierczak says that was the only thing the recipients had in common.
Kazmierczak says about 5 percent of mice, hamsters and other rodents carry LCMV and about 2 percent of the general public has antibodies to it, which means they have been exposed to it at some stage.
The virus usually causes little or no illness in healthy people, but can be deadly for those with weak immune systems like cancer patients and transplant recipients, who take immune-suppressing drugs to keep them from rejecting their new organs.
Donated organs are routinely tested for many viruses but there is no commercial test for LCMV. The CDC, state health officials, the Food and Drug Administration and others are investigating.
In an attempt to reassure people who need transplants, Rhode Island health director David Gifford says this is an extremely rare and unusual event.
Kuehnert however is advising doctors to watch for unusual illnesses in patients who recently had blood transfusions or transplants.
Wisconsin officials in explaining why they made no public statements in 2003, say the evidence was tenuous and as the virus doesn't spread person-to-person it was not considered a public health risk.
Dr. Staci Fischer, infectious disease physician for the transplant group at Rhode Island Hospital, discovered the infection in April, when two of her kidney transplant patients developed flu-like symptoms. One survived, but the other did not. She said she did not find out about the Wisconsin cases until too late to save her patient's life.
Fischer says after searching through medical literature and asked colleagues around the country if they had heard of anything similar, it wasn't until she called the CDC that the connection to LCMV and the donor's hamster was made. She says that knowledge would have made a difference.
According to the Rhode Island Department of Health, two patients in Massachusetts one a double lung recipient, the other a liver recipient also died within weeks of the transplants, which were performed on April 10 and April 11.
Kuehnert says two people who received corneas from the same Rhode Island woman in operations outside the United States are being monitored for signs of illness, he declined to say where the corneas were sent.
The donor's hamster was bought at a Petsmart store in Warwick, and Gail Mastrati, a spokeswoman for the state Department of Environmental Management, said the agency removed 102 hamsters, mice and guinea pigs from the store in the past week. The animals were euthanized and shipped to the CDC in Atlanta, where all will be tested.
Bruce Richardson, a spokesman for the Phoenix-based chain said it has asked the suppliers of rodents to the Warwick store to test their animals. He says not all of its vendors are affected.
Richardson would not say how many animals will have to be tested as it is not clear whether the hamster, which has died, was infected with LCMV when it arrived at the organ donor's household .He says to his knowledge they did not sell any sick hamsters.