A pet store chain linked to a rodent virus that killed three human transplant patients said Tuesday it is testing its breeding stocks of hamsters, guinea pigs and mice for signs of the virus.

Three patients died from the lymphocytic choriomeningitis (search) virus after receiving organs from a single donor, health officials said Monday. They believe the donor may have contracted the virus from a hamster purchased at a Petsmart (search) store in Warwick.

A spokesman for Phoenix-based Petsmart said the company is having its hamsters, guinea pigs and mice tested.

"We're taking samples of the breeding stock and also some of the juvenile pets from our vendors for testing," spokesman Bruce Richardson said.

He said the chain regularly tests for other diseases but not LCMV because it is rare. Richardson also noted it is not clear whether the hamster, which has died, was infected with LCMV when it arrived at the organ donor's household.

"To our knowledge, we didn't sell any sick hamsters," he said. There also are no indications of an LCMV outbreak among the chain's suppliers, he said.

Health officials removed dozens of hamsters, mice and rats from the Warwick store.

LCMV is commonly found in house mice but usually produces only flu-like symptoms in humans. It has also been associated with neurological illness and miscarriage in pregnant women.

In this case, however, the victims were transplant recipients who were taking very large doses of immune system-suppressing medication, which can allow viruses to multiply and cause an "overwhelming infection," state health director David Gifford said.

A few weeks after the transplants in mid-April, three patients died: a liver recipient and a double-lung recipient, both from Massachusetts, and a kidney transplant recipient from Rhode Island. Another Rhode Island patient who received a kidney became ill, but is recovering.

Public health officials who announced the deaths Monday said it was only the second documented case of LCMV being spread through an organ transplant and stressed its rarity in humans.

"We would encourage people who are on the (transplant) waiting list not to be concerned with this," Gifford said. "This is an extremely rare and unusual event."

Gifford did not identify the patients.

The double lung transplant was performed at Brigham & Women's Hospital in Boston, the liver transplant at Massachusetts General Hospital in Boston and both kidney transplants at Rhode Island Hospital in Providence, officials said.

Gifford said there are no plans to test other donor organs for the virus since it is so rare and testing could take several days, potentially making the organs unusable. He said he believed there was no commercially available test for the virus.

Two patients outside the United States received corneas from the Rhode Island donor, and officials of the federal Centers for Disease Control and Prevention said they are investigating where those corneas went.

Only one previous instance of LCMV causing a transplant-related death has been reported — in Wisconsin in December 2003 — but it wasn't definitively linked to rodent exposure, said Dr. Matthew Kuehnert of the CDC.

CDC investigators were testing the dead hamster to confirm the virus as the cause of the recent deaths. "We believe the hamster was the source, but we can't rule out a common house mouse," said CDC spokesman Dave Daigle.