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Date: Fri, 6 Sept 2002
Posted by: Lois Levitan (lcl3@cornell.edu)

1) Comments on Sept 6 NYTimes Opinion Piece and article about WNV Risks to the US Blood Supply
2) Text of the Sept 6 NYTimes Opinion Piece
3) Text of NYTimes article "Doctors confirm West Nile in a 4th transplant patient"

(1)
Today's NYTimes has an opinion piece and an article, both addressing the current investigation re: the possibility of WNV transmission by means of organ transplant and blood transfusion. Both are based on information from a Sept 5 CDC News Release (http://www.cfe.cornell.edu/ERAP/WNV/WNV-LArchive/9-4-02.html).

The CDC News Release confirms that the donor (who died in the hospital from injuries sustained in a car crash) and all 4 organ recipients have tested positive for WNV infection, 3 of them having developed encephalitis (1 fatality, 2 in hospital) and one showing milder symptoms. CDC interprets this as strong evidence, but not "proof" that these infections were transmitted by the organs rather than by mosquito bites.

The second issue under investigation is how the organ donor herself became infected with WNV, since blood tests taken when she was admitted to the hospital, but before she received blood transfusions, do not indicate she was WNV-positive. This is the evidence that suggests she may have been infected by blood transfusion.

The NYTimes opinion piece (#2 below) addresses the risk of transmission via the blood supply. I believe the Times has misinterpreted some important facts (or best understanding) about risks from WNV. In the 3rd paragraph the NYTimes says: "The federal estimate of roughly one or two West Nile cases per 10,000 transfusions is probably too high. Otherwise we should have seen scores or even hundreds of such incidents by now."

However, these 1-2 cases per 10,000 transfusions translate into 450-900 cases* of West Nile Virus infection, NOT cases that manifest clinical disease symptoms. As noted in a posting to this listserv on Sept 4: "Although rates of serious illness and death would likely be higher in this subpopulation than among the general public, we can perhaps calculate a ballpark estimate of the number of serious illnesses and fatalities attributable to receiving infected blood by looking at data from previous years when about 1 infected person in 150 developed serious illness, and about 12% of those died." (Source: http://www.cfe.cornell.edu/ERAP/WNV/WNV-LArchive/9-4-02.html)

Thus one might expect some 3-6 cases of WNV encephalitis per year in the US that could be attributed to blood transfusion from a donor infected with WNV and some 100-200 mild cases of the flu that might or might not send someone to the doctor and would likely not show up in a database of WNV-related illnesses. It therefore seems entirely plausible that the CDC risk estimate is accurate, and that the risk this presents to the nation's blood supply is in fact quite small.

* We derive this number from the NYTimes figure for numbers of people receiving blood transfusion. If we used the CDC figure of 13 million units of blood collected per year in the US, we might expect 1300-2600 infections attributable to blood transfusions, with at least 9-17 cases of WNV encephalitis and perhaps several hundred cases of mild flu.

(2)
NYTimes Opinion Piece, September 6, 2002

WEST NILE VIRUS AND THE BLOOD SUPPLY

The possibility that the West Nile virus might be spread through blood transfusions is disquieting given the lack of a rapid, reliable test to screen it out of the blood supply. But the risk, if it exists, is apt to be slight and is surely no reason to forgo receiving a lifesaving blood transfusion.

The focus of concern is a case in which four patients who received organ transplants from an accident victim later came down with the virus. The donor turned out to have had West Nile virus herself, and it seems likely that the transplant recipients got the virus either from the organs or possibly from the blood suffusing them. The donor, in turn, had received transfusions of blood from some 60 individuals, making it possible that she got the virus that way, although she may also have acquired it from a mosquito bite.

Given the new public awareness of the danger of West Nile virus, and the weakened condition of transplant recipients, the story has obviously raised concern. But what risk the virus might pose to the 4.5 million Americans who receive blood transfusions every year is difficult to determine. The federal estimate of roughly one or two West Nile cases per 10,000 transfusions is probably too high. Otherwise we should have seen scores or even hundreds of such incidents by now. Related viruses, such as those that cause dengue fever, St. Louis encephalitis and yellow fever, have no history of transmission through blood transfusions, and the West Nile virus, in areas abroad where it is prevalent, is not known to be transmitted in that manner.

Investigators hope to learn more soon about how the organ donor and another transfusion recipient, in Mississippi, got the virus. Then they will need to reassess the magnitude of the risk and whether a rapid screening test needs to be developed - a task that could take months or even years.

(3)
September 6, 2002  NYTimes
DOCTORS CONFIRM WEST NILE IN A 4TH TRANSPLANT PATIENT
By DENISE GRADY

Doctors have confirmed that a woman in Florida is the fourth person to have contracted West Nile virus after receiving an organ transplanted from a single donor who had the virus, a federal health official said last night.

Finding the virus in all four organ recipients "very strongly suggests" that the disease was transmitted by the organs rather than by mosquito bites, said the official, Dr. Lyle Petersen, a West Nile expert at the Centers for Disease Control and Prevention.

The Florida woman, 71, who has not been identified, had a liver transplant at a Jacksonville hospital and then came down with a mild illness but did not develop encephalitis. She is recovering at home in Miami.

The three other transplant patients did develop encephalitis, and one has died; the two others are still hospitalized.

The case has also raised the possibility that the virus was transmitted by blood transfusions as well as organs. The organ donor, injured in a car accident, received many transfusions before she died. She was not known to be ill before the crash, and a preserved sample of her blood, taken before she had any transfusions, was free of the virus. But further tests are still needed to find out whether she was infected by the transfusions or by a mosquito, Dr. Petersen said.

Speaking at a news conference, Dr. Petersen said the disease centers had also begun investigating a second case of possible transmission of West Nile virus by blood transfusions. In that case, a Mississippian developed a West Nile infection almost four weeks after receiving transfusions, well within the incubation period for the disease. The patient had also had numerous mosquito bites, however.

Remaining blood products from donors to that patient have been withdrawn from use. A spokesman for the Mississippi Health Department said 18 units of blood were involved. Health officials said they were preparing to contact the donors, as well as other recipients, to test them for West Nile virus.

But Dr. Petersen and Dr. Jesse Goodman, an official of the Food and Drug Administration, said that even if the cases were linked to transfusions, that route of transmission would most likely prove to be extremely rare. They emphasized that mosquitoes caused nearly all cases of the disease, and said current screening procedures would help protect the blood supply, by rejecting people with fever or any other symptoms of viral illness. In addition, people who are infected with West Nile have the virus in their blood for only a short time, unlike people with H.I.V. or hepatitis C, who may carry those viruses for life.

The officials also said the methods used to process plasma products, though not whole blood, destroyed many viruses, probably including West Nile.

Dr. Petersen said that as of yesterday, there were 854 reported cases of West Nile virus infection in 28 states and the District of Columbia. Louisiana and Illinois have had the most cases. There have been 43 deaths.

In about 80 percent of the reported cases, the patients have developed brain infections, either encephalitis or meningitis, Dr. Petersen said.

For every serious case that causes meningitis or encephalitis, researchers estimate, as many as 150 other people may be infected but have only mild symptoms. That means that tens of thousands of Americans may be infected, Dr. Petersen said. He also said that people who have been infected most likely develop long-lasting immunity to the disease.

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-- 
Lois Levitan, PhD       Program Leader
Environmental Risk Analysis Program
Center for the Environment
213 Rice Hall, Cornell University
Ithaca, New York USA 14853-5601

Phone:   (607) 255-4765     Fax: (607) 255-0238
Email:	LCL3@cornell.edu

Program Email: envrisk@cornell.edu
Web:http://www.cfe.cornell.edu/ERAP

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