In the wake of investigations into possible transmission of West Nile virus through human blood and organ transplants, medical experts are developing ways of protecting patients.
The Centers for Disease Control and Prevention reported Sept. 20 that it is investigating seven cases in which seven individuals developed West Nile after receiving blood transfusions, organ transplants or both. Two of these cases included fatalities. Additional potential cases via this route of transmission have been reported.
Thomas Yuill, UW-Madison professor of pathobiological sciences, said blood bank officials must have known there was some risk of this kind of transmission.
\I'm sure that they must have realized that it was possible, but, given the small number of human cases, the probability was so low as to be negligible,"" Yuill said.
Donated blood is not currently tested for WNV. However, Laura Moon, communications supervisor for the Badger-Hawkeye region of American Red Cross Blood Services, said the organization makes every attempt to prevent infected blood from ever being collected.
""The donor screening process will prevent people who aren't feeling well [from donating]. That is our focus at this point until a screening test is available,"" Moon said.
However, predonation screening is not 100 percent effective.
""The virus is sort of slow in getting started,"" Yuill said.
According to Yuill, someone with the virus would have no way of knowing not to donate until they develop symptoms.
""It would be a matter of hours to a couple of days, so it's not a prolonged kind of period,"" Yuill said. ""Good reliable data on that period of time aren't available because, of course, you can't do experiments with people to answer that question. You'd have a tough time finding volunteers for that.""
However small the chances of transmission during this critical period, the Food and Drug Administration, which is responsible for the safety of the nation's blood supply, acknowledges there is a risk. It is currently working with blood banks to re-evaluate current procedures for reporting post-donation illness.
Preliminary research is already in place; blood in mosquitoes and dead birds can already be tested for antibodies to the virus. The remaining work requires that these tests be adapted to fit in with existing blood screening processes, namely to detect the presence of the virus itself, even before an exposed individual develops antibodies. The new tests would also need to be cost- and time-effective; screening enough blood to help approximately 4.5 million Americans each year is no small task.
In the mean time, blood and organ recipients can take some solace in the fact that WNV exposure through donated blood or organs is not any more dangerous than exposure from an infected mosquito. It still only poses a significant threat to those with compromised immune systems. If an otherwise healthy person receives WNV-infected blood after routine surgery, his or her risk ""wouldn't suddenly shoot up,"" Yuill said.
Individuals who have surgery planned but are still fearful of donated blood do have another option available.
""Many surgeons encourage patients to donate blood ahead of time for themselves to avoid these kinds of concerns,"" said Kathryn Vedder, director of the Madison Department of Public Health.
However, those responsible for the nation's blood supply are still confident in its safety.
""We have a remarkably good blood screening system here in the United States, probably the best in the world,"" Yuill said.
