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West Nile Virus & Organ Transplants
Date:
Tue, 3 Sept 2002 [Edited Wed, 4 Sept 2002].
Posted by:
Lois Levitan (lcl3@cornell.edu)
Labor Day Weekend 1999 brought first news of West Nile Virus in the Americas.
Labor Day Weekend 2002 brings news of another risk related to WNV, with the as-yet-unconfirmed evidence that the virus can be transmitted via organ transplant or possibly by blood transfusion from an infected person. While this speculation adds a wrinkle to the set of assumptions about disease transmission, it should be noted that even if confirmed, the general population is at no greater risk of contracting WNV than previously thought.
The news about the potential for transmitting WNV via organ transplant does make us aware that a sub-population of people about to undergo high risk organ transplants and/or receive blood transfusions may be at still greater health risk because (a) it is difficult to know whether a donor has WNV circulating in their blood system and (b) transplant patients are given immune suppressing drugs to prevent rejection of the donated organ. The immune-suppressed are more vulnerable to WNV infection and serious illness. However CDC health officials point out that the additional risk of contracting WNV is quite small in comparison with the much larger risks from these medical procedures.
In the Sept 2 NYTimes article on this subject, CDC and FDA officials are said to have calculated the risk of transmitting WNV through blood transfusions in the range of 1 to 2 cases per 10,000 transfusions. With about 13 million units of blood collected each year in the US, this implies that 1300 - 2600 infections per year could be transmitted via blood transfusions, if this is shown to be a viable means of transmission. 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 receipt of 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: Thus one might expect at least 9 - 17 cases of WNV encephalitis per year in the US could be attributed to blood transfusion from a donor infected with WNV.
In the second of the articles copied below from the Sept 1 and Sept 2 NYTimes, CDC and FDA officials are said to have calculated the risk of transmitting WNV through blood transfusions in the range of 1 to 2 cases per 10,000 transfusions. With about 13 million units of blood collected each year in the US, this implies an additional 1300 - 2600 infections per year. 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 additional serious illnesses and fatalities by looking at data from previous years when about 1 infected person in 150 developed serious illness, and about 12% of those died: Thus one might expect at least an additional 9 - 17 cases of encephalitis per year in the US.
---------------------------------- NY TIMES [edited] September 1, 2002 HEALTH OFFICIALS STUDYING WEST NILE-TRANSPLANT By LAWRENCE K. ALTMAN
Three of four patients who received organs from one donor have apparently developed encephalitis and tests show that one recipient is infected with the West Nile virus, raising suspicion that the virus can be transmitted through organ transplants, federal health officials said yesterday.
One of the four recipients died about four weeks after the transplant. Standard pathology tests from an autopsy show that the recipient had encephalitis, or inflammation of the brain and central nervous system. Tests are planned to determine if the recipient was infected with West Nile virus, which causes encephalitis.
Tests have shown that another recipient, a 63-year-old man who lives in Miami-Dade County, Fla., has West Nile fever.
Because the organ donor received a number of blood transfusions before dying in Georgia on Aug. 1, health officials are also investigating the possibility that the virus can be transmitted through blood.
Federal health officials said they were taking the situation seriously and were aggressively investigating the cluster of cases over the Labor Day weekend. The reason is that if additional tests confirm that the three recipients developed West Nile encephalitis, it would be a new route of transmission of the virus, which was first identified in this hemisphere in 1999, in New York City.
No case of transmission of West Nile or closely related mosquito-borne virus through blood or organ transplants has been reported in this country, said Dr. James M. Hughes, a top official of the Centers for Disease Control and Prevention in Atlanta.
On Friday night, Dr. Julie L. Gerberding, the director of the C.D.C., said that "transmission of the West Nile virus through blood and organs is biologically plausible" and that "a leading hypothesis that we are investigating is that it is related to the organ transplant."
Dr. Gerberding's agency is responsible for protecting the public's health from infections like West Nile fever.
Scientists have performed statistical analyses that show that transmission of West Nile virus could occur at a very low rate through blood transfusions, Dr. Gerberding said.
The donor and the four recipients are from Georgia and Florida, where the virus is known to have infected mosquitoes, birds and humans. Health officials said they were working to rule out a remote chance that all developed their illness from mosquito bites.
Dr. Hughes said in an interview that "several dozen" state and federal epidemiologists, laboratory scientists and other health workers had been thrust into the medical investigation.
Some are working to obtain additional information about the donor's health before dying on Aug. 1 from injuries suffered in a traffic accident.
The transplants were performed on Aug. 2 and 3, Dr. Hughes said. One patient received the donor's heart, a second patient received the liver and two patients each received one kidney.
One of the kidney transplant recipients died, Dr. Hughes said.
Two of the organ recipients went home after surgery but returned when symptoms of encephalitis developed, Dr. Hughes said. The man in Florida did not leave the hospital. [Note: This fact provides some of the evidence for the organ transmission hypothesis, because it is not likely that the man was exposed to mosquitoes in the hospital, and the incubation period -- from mosquito bite to showing symptoms -- is typically 3-14 days.--LCL]
Other members of the team are being sent to a number of locations to collect tissue and blood specimens that will be sent to state laboratories and to a C.D.C. laboratory in Fort Collins, Colo., that specializes in infectious agents that are transmitted by insects. One aim is to conduct all tests with the same, standard technique to ensure validity of the findings.
Meanwhile, scientists at the C.D.C. are conducting special laboratory tests on the brain of the kidney recipient who died for evidence of West Nile virus or a closely related virus.
The medical investigators are about to begin tracing the individuals who gave the blood that the organ donor received before death.
Blood banks routinely keep a small amount of a donor's blood for testing in the event that infections or other complications develop among recipients of a donor's blood. Such tests have not been performed yet, Dr. Hughes said.
Also, the investigators are seeking any blood from the donor that may have been stored from before the time the donor received blood transfusions to determine if the recipient was infected with West Nile.
[... SNIP...] As is standard for organ transplant recipients, all four recipients received immune suppressing drugs to prevent rejection of the donated organ. The weakened immune status leaves such patients more vulnerable to infections and, in such cases, to more serious illness.
One of the four organ transplant recipients developed a mild fever that resolved. Tests are planned to determine whether that recipient had a mild case of West Nile fever. Most people infected with the virus develop a mild flu-like illness or experience no symptoms.
If blood donations are confirmed as the source of the transmission, it would raise questions whether blood banks would need to test blood for the West Nile virus before it is transfused. Blood banks routinely test for viruses and bacteria that cause hepatitis, AIDS and other infections.
But, Dr. Gerberding said, "the problem is that we do not have a rapid test for West Nile virus," and other tests, like the PCR (for polymerase chain reaction), are not reliable for screening blood at this time [... SNIP...]
------------------------------------------------------------------------ September 2, 2002 LINKING WEST NILE and TRANSPLANTS MAY TAKE WEEKS By LAWRENCE K. ALTMAN
It will take at least two weeks to determine whether the West Nile virus was transmitted through organ transplants or blood transfusions to a cluster of four transplant recipients in whom encephalitis has been diagnosed or suspected, federal health officials said yesterday.
But the unproved yet real possibility that transfusions had transmitted the disease had the officials yesterday acknowledging this concern: there is no rapid test to screen donated blood for the West Nile virus. It will take at least months to conduct the research to develop a reliable test, they said.
Until there is a test, they said, blood donors and recipients will have to consider the theoretical risk that receiving a transfusion or transplant could expose them unwittingly to West Nile.
The officials insisted, however, that the nation's blood supply was safe, and that the risk of acquiring the virus was surely the least concern for anyone needing blood or a new organ. The risk of transmitting the virus through blood transfusions is calculated to be low - in the range of 1 to 2 cases per 10,000 transfusions, officials from the Centers for Disease Control and Prevention in Atlanta and the Food and Drug Administration in Washington said. About 13 million units of blood are collected each year in the United States.
Because blood is involved in the natural transmission of West Nile - through mosquito bites - doctors have theorized that West Nile could be transmitted through transfusions and organ transplants. Two weeks ago, health officials said they reminded the nation's blood banks to enforce a standard procedure - rejecting donations from patients with fever and flulike symptoms, which could be symptoms of mild West Nile fever.
But the chief executive of the New York Blood Center, Dr. Robert L. Jones, said that if transfusion transmission of West Nile virus was confirmed, blood bank officials might have to ask about a history of mosquito bites. That step could vastly reduce, if not deplete, the number of donors, and aggravate an already serious shortage of blood in the country. Dr. Jones and the officials urged the public to donate blood.
The concern arose in recent days when health officials learned that a transplant recipient had developed West Nile encephalitis. That case sparked an investigation that has found the cluster in Georgia and Florida from a single organ donor, raising suspicion that the virus could be transmitted through organ transplants or blood transfusions or both.
This year, the nation is experiencing its worst outbreak of West Nile fever since the virus was first detected in this hemisphere, in 1999 in New York City. Over the weekend, the total number of cases has risen to 638, including 31 deaths.
Preliminary tests of a patient who died with encephalitis after receiving a kidney from the donor show evidence of infection with a mosquito-borne virus. Further tests are needed to prove it is West Nile virus.
On Friday night, the C.D.C. director, Dr. Julie L. Gerberding, said her agency was taking the situation seriously because of significant concern about the possibility of transmission of virus through blood. But as of yesterday it was premature to conclude that blood transfusions were the source of the donor's infection.
In recent days, the centers asked doctors and hospitals to report possible cases of West Nile fever through blood and organ transplants to their local health departments. A concern is that because most people who are infected with the virus experience no symptoms, they could donate blood without knowing they have it.
If so, the period of transmissibility is likely be short, "a few days to a couple of weeks at the most," Dr. Jesse Goodman, an F.D.A. official said. But, he added, "in an unfolding situation, we don't want to be speculative or pretend that we have exact or precise information."
Dr. Goodman said he would not expect people who have recovered from an infection to have West Nile virus in their blood for long because by the time symptoms develop, the virus is difficult to detect. In such cases, evidence of West Nile infection is based on detecting the specific antibodies that a patient's immune system develops in response to the infection. "It is very important to recognize that unlike H.I.V. or hepatitis, West Nile virus is an acute infectious disease and we are unaware of any kind of chronic carrier state," Dr. Goodman said.
Asked if health officials could assure Americans that the nation's blood supply is safe from West Nile virus, Dr. James M. Hughes, a top C.D.C. official, said: "We can't give guarantees. We think we have a very safe blood supply."
He also said: "If I were a person with severe chronic disease and I needed an organ transplant, concern about this would be right at the bottom of my list of things that I was worried about. Similarly, if I needed a transfusion this would be at the bottom of the list of my concerns. If I lived in an area where West Nile was circulating, which is much of the country at the moment, my greatest concern about West Nile would be to take precautions to minimize my risk of being bitten by mosquitoes."
Dr. Jones of the New York Blood Center said the threat of transfusion-borne West Nile virus had to be taken seriously. The New York area relies on blood imported from Europe and elsewhere in the United States, including the South, where West Nile is a particular problem this year.
Federal officials have urged blood centers to exclude donors who lived in England and other foreign areas where mad cow disease has occurred. Such exclusions have depleted donations in New York City by 25 percent this summer, Dr. Jones said.
He added that every medical procedure carried risks. "If we were to guard against every risk, theoretical or otherwise, we would have no blood supply, and patients who need blood would suffer the consequences," Dr. Jones said.
Available tests for West Nile virus are intended to detect infections in symptomatic patients and have not been rigorously assessed for their ability to detect the virus in people without symptoms, which would become important if the organ donor became infected through a blood transfusion, Dr. Goodman said.
Copyright 2002 The New York Times Company
-- 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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