CDC: Colorado man's West Nile virus death likely caused by infected blood transfusion in hospital

DENVER - A Colorado cancer patient died from West Nile virus in 2012 and investigators say he probably was infected by a blood transfusion at a hospital, according to the Centers for Disease Control and Prevention.

This is the first probable case of transfusion-associated West Nile virus infection in which a blood donation tested negative on an initial screening test, according to a CDC report on the death in the Morbidity and Mortality Weekly Report released today.

The patient has not been identified.

Starting in 2003, the U.S. blood supply has been screened for West Nile virus. Since then, approximately 3,500 West Nile virus-infected blood donation units have been removed from the blood supply nationwide and only 12 cases of transfusion-associated transmission of West Nile virus have been identified, CDC says.

This is the second suspected case of a person dying from a blood transfusion contaminated by West Nile virus in the United States. The first death happened in 2004.

In August 2012, a Colorado man with non-Hodgkin’s lymphoma was admitted to Presbyterian/St. Luke's Medical Center in Denver for chemotherapy and a stem cell transplant, according to CDC and hospital officials. His cancer was in partial remission after six cycles of chemotherapy.

After 18 days in the hospital, the patient developed gastrointestinal symptoms. He had received blood transfusions and the stem cell transplant during that time. He later developed fever, suffered respiratory failure and was placed on mechanical ventilation, CDC says. 

He died after 47 days in the hospital and an autopsy confirmed he died from West Nile virus-related encephalitis, CDC says.

Presbyterian/St. Luke's officials told 7NEWS the infected blood donation was donated by a person at the medical center.

Bonfils screens blood for the hospital and tested the implicated blood donation as part of a "minipool" of six donations from different people, said Bonfils Medical Director Dr. Tuan N. Le said. Testing a pool of donors is more efficient and cost-effective, Dr. Le said.

The test of the minipool blood sample was flagged by a screening test as possibly carrying West Nile virus, Dr. Le said. The blood bank then used a more sensitive test to screen each of the six individual blood donations in the minipool, but the tests were negative for West Nile virus.

Following Food and Drug Administration guidelines, Bonfils cleared the donated blood for release into the blood supply, CDC said.  

The infected blood donor was unaware of having West Nile virus and had no history of illness, before or after giving blood, the CDC said. However, later investigation by public health officials found the donor had been been bitten by mosquitoes while outdoors.   

Dr. Le called the cancer patient's death an "unfortunate perfect storm."

A seemingly healthy person, unknowingly infected with West Nile virus, donates blood, Dr. Le said. And a more sensitive test can't confirm the virus's presence in the donor's individual blood sample -- possibly because there was only a low concentration of the virus.

Medical investigators believe the cancer patient with a weakened immune system was likely more susceptible to infection from a very low concentration of West Nile virus in the blood transfusion, CDC says.

To combat such risks, Bonfils has adopted a new protocol. If a six-donor minipool tests positive for West Nile -- but tests of individual donors contributing to the pool don't confirm the virus -- Bonfils will now throw out all six donations, Dr Le said.

If testing of both a six-donor minipool sample and one of the contributing donor's individual samples are positive for West Nile, Bonfils will only test single donor samples in the county where the infected donor lives for 14 days, Dr. Le said. This more sensitive testing of individual donations should more effectively identify West Nile-infected blood -- even when the virus is in low concentration, Dr. Le said.

If testing of single-donor samples are negative for 14 days, the blood bank will switch back to testing blood in minipools.

 While the CDC says West Nile virus infections from blood transfusions are rare,  it is advising healthcare providers to consider West Nile virus disease in any patient with compatible symptoms who has received a blood transfusion during the 28 days before the onset of illness.  Possible cases should be promptly reported to the blood collection agency and public health authorities, the CDC says.