Virus a Risk to Blood Supply

Concerned that undetected cases of West Nile virus are putting the state’s blood supply at risk, officials have stepped up testing of donated blood.

The move to a more rigorous screening process comes after tests last month found that about one in 1,000 people who gave blood in Los Angeles County had West Nile and one in 400 donors in San Bernardino County were infected.

Officials don’t believe that any West Nile-tainted blood has been shipped to hospitals. But the stakes are high, they said, because recipients of blood tend to be elderly and frail people who are most vulnerable to the disease.

“If those patients, say, the elderly person with leukemia, got a contaminated unit with West Nile, they would be doubly vulnerable,” said Dr. Janice Nelson, medical director of transfusion medicine at Los Angeles County-USC Medical Center. “They would probably die of West Nile virus.”

Cases of West Nile infections and deaths through transfused blood are extremely rare. However, in Arizona about two weeks ago, a man in his 40s died months after receiving West Nile-infected blood during a transfusion. The blood had been donated in early June just before Arizona toughened its testing policies.

More than 370 Californians have tested positive for the virus and 11 people have died, but state officials believe that thousands more have West Nile and don’t know it. Nelson and others said the rate of blood donors who had the virus showed how much it had spread.

“For every person reported with West Nile, there’s many, many people who have West Nile who are never reported,” said Jonathan Fielding, director of public health for the Los Angeles County Department of Health Services. “There’s definitely thousands of cases of West Nile in L.A. County.”

People are infected by mosquitoes that carry the virus. Cases can feel as mild as a simple itch, escalate into a fever and headaches, and, less than 1% of the time, eventually cause death. About 80% of those who become infected don’t experience symptoms.

Until recently, the Red Cross and other blood bank operators tested pools containing the blood of multiple donors. But under the new rules, officials will test each individual donation. Any blood with West Nile will be tossed out.

State officials have confirmed that 39 blood donors were infected with West Nile. Five of them later showed symptoms of the disease. Many of those cases have been detected in the last few weeks as the virus has spread from the Inland Empire into Los Angeles and Northern California.

That number might soon increase. San Bernardino County, for example, said it recorded 39 donors who tested positive for West Nile in August, but those tests must be double-checked by the blood banks before they become official.

State officials hope that the increased testing will prevent any West Nile-infected blood from reaching hospitals and other medical facilities. West Nile experts said the results of the blood testing showed how healthy people could have the virus and never know it. Donors who are infected generally have low levels of the virus.

“Our estimate is that one out of 1,000 people is infected with the West Nile virus and that these results are indicative of the underlying infection rate in the population at large,” said Dr. Ross Herron, medical director of the American Red Cross Blood Services, Southern California Region.

West Nile has killed more than 600 people across the United States since it arrived in North America in 1999. Most of the victims were either elderly or had a history of serious illness.

Because there is no cure for West Nile, health officials urge those of all ages to take precautions.

People should wear insect repellent containing DEET and cover up with long sleeves and pants when outside, particularly at dusk and dawn, when mosquitoes are most active.

Vector control experts believe that West Nile will continue to spread until late October, when it’s expected to taper off.

In San Bernardino County, officials said the last few days had been encouraging.

“Just looking at our numbers, we actually see a slowing down now,” said Dr. Frederick Axelrod, chief executive of the Blood Bank of San Bernardino and Riverside Counties. “We think things are slowing down a bit. We think we might have reached the peak.”