West Nile-Like Positive
Blood Donor In Canada

From Patricia Doyle, PhD

Monitoring the blood supply is a very positive step in the battle against West Nilelike Virus. Jeff, you and I both advocated doing so as far back as Spring 2000. As the virus becomes more ingrained in the population we will probably see a substantial number of cases found via this method. It is also necessary to protect the fragile folks who will receive the blood. Anything we can do to make the blood supply safer is a positive step.
From ProMED-mail
Saskatchewan: West Nile Virus-Positive Blood Donor Is First Human Case
Saskatchewan has confirmed Canada's first domestic case of West Nile virus in a human this year. It is also the first time a person has contracted the virus in Saskatchewan. Provincial health officials announced the case on Fri 25 Jul 2003, saying only that the person was from Assiniboia, 130 kilometres southwest of Regina. They did not give the person's age or say whether the person was male or female. However, sources say the person is a man.
"Fortunately this person is one of the majority who didn't get ill," said Eric Young, Saskatchewan's deputy chief medical officer. "However, I think it just brings home the fact that people have to take precautions, they have to take the potential for West Nile seriously and they have to do the things they can to reduce that risk."
On Thursday, Ontario officials announced that province's first probable case of the 2003 season but said the person likely contracted the disease while on a trip to the United States. "We knew it was only a matter of time before someone in Saskatchewan became infected," said Dr. Ross Findlater, the province's chief medical health officer. "We are entering a period where there are more of the mosquitoes that carry West Nile virus."
The virus was found in a unit of blood donated in the province on Tuesday, the Canadian Blood Services reported in a news release. "He was well when he donated and remains well," said Ted Alport, medical director of Canadian Blood Services Saskatchewan. Once the blood tested positive for the virus, it was withdrawn from inventory and the donor, who has been notified, will not be eligible to donate blood again for 56 days, at which time the virus will no longer be present.
"This result shows that our West Nile virus test is doing exactly what it was designed to do -- helping reduce the risk that the virus will enter the blood supply," Dr. Graham Sher, chief executive officer of Canadian Blood Services, said in the release. But since this person had no symptoms, Dr. Donald Low, a leading expert in infectious diseases, said he expects this is simply the first detected case of a person contracting West Nile virus infection, not the only person to have the disease. "If we've detected one case in a blood donor, then we're sure that there are more cases out there that have gone unrecognized," said Low, a microbiologist at Mount Sinai Hospital in Toronto.
There were 416 probable or confirmed cases of West Nile virus in Canada in 2002, although officials acknowledge that was probably just the tip of the iceberg. It's believed 80 percent of people who get the virus have such mild symptoms they aren't even aware they've been infected. Dr. Mike Drebot, head of the viral zoonosis section of Health Canada's National Microbiology Laboratory in Winnipeg, said it is difficult to predict what the Saskatchewan case means for the province or the rest of Canada. "We may see cases in a number of provinces or maybe we'll see the majority of cases in only one or 2 provinces -- it's really difficult to say. "But the risk for cases wherever we've detected West Nile activity, and this ranges from Alberta even to New Brunswick, is there. Although in certain jurisdictions, the risk may be higher than in others.
"I would hope that with all the public education that's been done as well as mosquito abatement procedures, that we'll be able to dampen the risk and we'll see fewer human cases than we saw last year." Last year, 20 deaths were attributed to West Nile virus infection in Canada: 18 in Ontario and 2 in Quebec. The 2 were the only provinces that recorded domestically acquired cases of the disease in 2002, the first year there were human cases in this country. 8 U.S. states have already reported a total of 12 human cases of West Nile virus so far this year: Alabama, Ohio, Texas, South Carolina, South Dakota, Minnesota, Colorado, and Iowa.
Birds play a pivotal role in the buildup of the virus in an area. Early in the season, mosquitoes become infected by feeding on infected birds. The mosquitoes then transmit the virus to other birds, building up a critical mass of virus in an area. That process is called amplification. When sufficient amounts of virus are found in the bird and mosquito populations of an area, mosquitoes that feed mainly on people can also become infected, transferring the virus into the human population.
To date, 69 dead birds have tested positive for West Nile virus in Manitoba and another 39 in Ontario. Dead birds have also tested positive for the virus in New Brunswick (one), Saskatchewan (17), Quebec (8) and Alberta (3).
[This circumstance mirrors the American experience (in the states of Colorado and Florida): that the surveillance of donations by blood banks is proving to be a sensitive indicator of the presence of West Nile virus infection in the human population, well before the first symptomatic cases make their appearance. In the Canadian situation, the surveillance of blood donations has revealed the first human case of West Nile virus infection in the province of Saskatchewan in the absence of overt disease. - Mod.CP]
[At the risk of a barrage of emails, the thought that comes to mind here is: so much for sentinel chickens... sentinel chicks may be better! - Mod.MPP]
Patricia A. Doyle, PhD Please visit my "Emerging Diseases" message board at: Zhan le Devlesa tai sastimasa Go with God and in Good Health



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