The projections are drawn from the Canadian Health Measures Survey, which actually tested the blood of people who took part to look for the viruses. They are based on data from 8,434 Canadians aged 14 to 79.
The study, published Wednesday by Statistics Canada, found 0.4 per cent of people surveyed were infected with hepatitis B and 0.5 per cent were infected with hepatitis C.
Half of the people with hepatitis B said they were unaware of the infection; 70 per cent of the people with hepatitis C said they did not know they were infected.
Experts have been warning that Canada is facing an unrecognized health-care crisis with hepatitis C, because undetected and untreated infections in the baby boom generation will trigger a surge in cases of liver failure and liver cancer.
The chairman of the board of the Canadian Liver Foundation suggests the new estimates are actually unhelpful, because they give a falsely reassuring sense of the scope of the problem.
"I think they're actually harmful, counterproductive. Because I think it's minimizing the true state of affairs," said Dr. Morris Sherman, a hepatologist (liver specialist) at Toronto General Hospital.
The survey estimates 138,600 Canadians have hepatitis C. But Statistic Canada's own website reports that the number of diagnosed cases of hepatitis C in the country — it is a reportable disease — is nearly 300,000, Sherman notes.
The Canadian Health Measures Survey is designed to test a representative sample of Canadians for a range of different conditions — things like high blood pressures, diabetes and obesity. It does not include First Nations people living on reserves, prison inmates, members of the Armed Forces or people living in some remote regions.
To get a good idea of the scale of the hepatitis B and C problems, the survey would need strong representation from certain population groups that typically don't agree to take part in this kind of a study, says Dr. Mel Krajden, a hepatitis C expert with the B.C. Centre for Disease Control.
Those groups include injection drug users, the homeless, First Nations people, prison inmates and immigrants from parts of the world where hepatitis B and C infections are more common than they are in Canada. Those include South Asia, China and Eastern Europe.
"The study wasn't designed to specifically understand the epidemiology of (hepatitis) B and C. Unless you sample these populations correctly, you may not accurately estimate what's going on," Krajden says.
He notes it is typically extremely hard to accurately sample these groups. In particular, immigrants from some parts of the world where rates of these infections are high may be distrustful of this type of study and refuse to take part, he says.
Krajden says British Columbia knows the hepatitis C status of about one-quarter of its population, because a lot of testing has been done there. About 1.4 per cent of the province's total population is hepatitis C positive; among baby boomers, where the risk is greatest, the rate is three per cent, he says.
Krajden says B.C. rates may be higher than other provinces, because there are higher rates of injection drug users there. While he called the new data "a step in the right direction," he too believes the estimates in this new report are artificially low.
In related news Wednesday, Janssen Inc. announced that Health Canada has approved its new hepatitis C drug Galexos, (its generic name is simeprevir).
Doctors who treat people with hepatitis C have been anxiously awaiting approval of this and another pending new drug as they are expected to be significantly easier for patients to take and should have a higher success rate.
But the new drugs are expected to be very costly, and experts worry that may slow their adoption.