West Nile risk spreads to blood and organ donations

With transmission by organ transplant confirmed and transmission by blood transfusion likely, experts balance the possibility of infection versus the potential impact on supply.

By Victoria Stagg Elliott, amednews staff. Oct. 7, 2002.

When the possibility of West Nile virus transmission by blood transfusion first came to light in early September, Louis Katz, MD, medical director of the Mississippi Valley Regional Blood Center conducted an unscientific survey.

He went to the lobby of the Davenport, Iowa, blood bank and asked people waiting to donate if they had been bitten by a mosquito lately, and, therefore, could possibly be carriers of the infectious agent. Nineteen out of 20 answered yes, proving how widespread possible exposure could be.

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Though Dr. Katz' survey was simple, it underscores what has become an increasing challenge: Figuring out a way to minimize the risks that could result from donated blood or organs that could have been infected with West Nile virus.

Specifically, efforts by the Centers for Disease Control and Prevention and the Food and Drug Administration have taken on a new imperative since experts confirmed that the infection can be transmitted by organ transplantation. The investigation into transmission by blood transfusion was still ongoing at press time. However, the possibility is considered likely enough that any remaining blood linked to the patients who came down with the virus after transfusion has been taken off the shelves.

"We believe there's sufficient evidence, when you put it all together, to say that there is likely a risk, that it is likely that at least some of the reported cases may be related to transmission by blood and, certainly in the one case, transmission through organ transplantation," said Jesse Goodman, MD, MPH, deputy director, FDA's Center for Biologics Evaluation and Research.

But West Nile presents a special dilemma for those procuring blood and organs for transfusion and transplantation. How do you balance the risk of transmission of an infectious agent with the risk that a lifesaving pint of blood or solid organ won't be available when someone needs it? The risk factors for West Nile are ubiquitous, and eliminating possible carriers would leave bare blood bank cupboards, already thinly stocked because of longstanding shortages. Organ transplants would grind to a halt.

No screening test exists for West Nile virus.

"Does the frequency and the morbidity justify action?" said Dr. Katz, also president-elect of America's Blood Centers, an umbrella organization for nonprofit blood banks. "At what point does a guy who comes into the emergency room after a car accident not have enough blood to get by because we've deferred donors for risks that certainly don't rise to the level of HIV or hepatitis B? Adequacy of the blood supply is a safety issue as well."

Since screening out high-risk donors would be impractical, the FDA announced in September that the agency will be working with blood banks to develop a means by which donors could alert officials if they become ill after donation. The blood could then be removed from the supply if necessary. Those with flu-like illnesses -- caused by West Nile or other infections -- are already banned from donating.

The United Network for Organ Sharing is asking transplant physicians to be aware that a flu-like illness post-transplant may be West Nile but will not be changing its screening protocols until a good test for the presence of the virus becomes available.

"What do you do if the person was bitten by a mosquito two days ago and is incubating this stuff and you don't know it?" said Lawrence Hunsicker, MD, medical director of the organ transplant service at the University of Iowa in Iowa City. "The answer is there's no way in God's green earth you're going to know about it."

The FDA is calling for rapid development of a test for the virus and has announced that the regulatory process will be sped up to get it to the market faster because without a good screening question for donors, the next best option is to screen the donation. Current tests only reveal the presence of an antibody, long after the virus has cleared itself from the body, making them useless to determine if the blood or organ will transmit the virus to its recipient.

Actual risk

But experts stress that the risk of contracting West Nile from donated blood or organs is extremely small and the nature of the virus is very different from other bloodborne pathogens that patients usually fear.

The acute nature of the virus means that the window of opportunity for a carrier to transmit it through donation is very small. It's also not as deadly as HIV or hepatitis. Of those who received possibly infected organs or blood, only one mortality is known to have resulted from the infection, according to CDC reports. West Nile is also not a chronic condition, and the other patients whose cases are under investigation are expected to recover.

4.5 million Americans receive blood products each year.

"It is important, as always, to keep a risk, even a poorly understood risk, in perspective," said Dr. Goodman. "There are approximately 4.5 million people in the United States who receive blood products each year, and both blood and blood products and organ transplantation are often lifesaving, or life-enhancing. For people who need a transfusion or transplant, our current knowledge suggests that the potential benefits will outweigh the risks, including the risk of West Nile virus infection."

The virus is also seasonal. Although West Nile has become a bigger and more widespread problem every year, it will be quiet for the next few months, allowing public health officials and those in the blood banking and organ procurement industries to prepare for the next round.

"We learned our lessons in the 1980s with HIV," said Dr. Katz. "The level of cooperation and communication between the FDA, CDC and the blood banks is better than it's ever been. Everybody's talking."

But some experts say an incident like this increases the pressure to consider other options. Several pathogen reduction technologies are in development, although none has yet to pass FDA scrutiny.

Some experts say that transfusions are used more liberally, and maybe they shouldn't be. Maybe bloodless surgical techniques should be considered more often, or the bar should be raised as far as balancing the risks and benefits of the procedure.

"We need to ask if the transfusion is really necessary, and if it is worth the risk," said Neil Blumberg MD, director of transfusion medicine at the University of Rochester Medical Center in New York.

ADDITIONAL INFORMATION:

Renewed vigilance

Experts say that this season's tally of nearly 2,000 cases of West Nile virus in locations across the country has ended the United States' long-standing complacency with mosquito-borne disease.

Neglected mosquito-control programs are being built up nationwide, and the public is increasingly reminded that a mosquito bite has the potential to be more than a mere annoyance.

"In many places, since we have not had large outbreaks of mosquito-borne diseases, people became complacent about the need to control mosquito populations," said Ed Thompson Jr., MD, MPH, health officer for the Mississippi State Dept. of Health. "Now, we're being reminded that you have to control mosquito populations, and you have to reduce mosquito bites. You can't forget about mosquitoes. They're still capable of transmitting diseases that can be serious in humans."

There is reason for the renewed vigilance.

First, West Nile. At press time, the Centers for Disease Control and Prevention had recorded 1,852 cases of West Nile, including 89 deaths.

In addition, the Virginia Dept. of Health announced in early September two cases of malaria in individuals with no history of international travel. This was an unusual finding because nearly all cases of malaria in the United States are acquired overseas.

"We're being reminded by West Nile virus, as we will by other diseases, that infectious diseases have not been conquered," said Dr. Thompson. "They are part of our environment, and we have to live with them and deal with them effectively.

Weblink

CDC West Nile virus basics (http://www.cdc.gov/ncidod/dvbid/westnile/)

FDA West Nile virus and blood safety (http://www.fda.gov/cber/safety/wnvbld.htm)

Article, "Public Health Dispatch: Investigation of Blood Transfusion Recipients with West Nile Virus Infections," Morbidity and Mortality Weekly Report, Sept. 13 (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5136a5.htm)