CALGARY -- With Alberta’s COVID-19 cases climbing, the amount of cases with an unknown source is also on the rise. One infectious disease expert says untraced cases will make it more difficult to prevent the spread of the virus.

“It’s a big concern,” said Dr. Craig Jenne with the University of Calgary’s department of Microbiology, Immunology and Infectious Diseases.

“You can imagine if there are this many untraceable sources, those all present a risk to hospitals, to long term care facilities, to patients who are at risk and trying to limit contacts,” Dr. Jenne said.

Dr. Craig Jenne

The province says a lot of the recent spread of COVID-19 is attributed to private gatherings and family events.

But 67 per cent of the cases reported between Oct. 27 and Nov. 2 were spread from an unknown source.

Of the 6,110 total active cases in Alberta as of Nov. 2, 52 per cent are unknown.

Alberta’s Chief Medical Officer of Health, Dr. Deena Hinshaw, admits the unknown cases are a concern. But she says contact tracing takes time and that’s why more of the recent cases are still listed as unknown.

“Because the volume of cases we've been seeing every day has been rising, and because when we get a new case reported, of course, a public health investigation has yet to take place,” Dr. Hinshaw said Wednesday.

Alberta introduced a mandatory social gathering limit of 15 people in Calgary and Edmonton just over a week ago and Dr. Hinshaw says they’re closely monitoring the effectiveness of those measures.

Premier Jason Kenney isn’t ruling out any more “targeted measures” in the near future. But determining the correct response can be more difficult without proper contact tracing, Dr. Jenne explained.

“We don’t know exactly which things are leading to the most infections, where we can target restrictions. As a result, we end up having to bring in broader restrictions instead of surgical strikes to reduce specific transmission events,” Dr. Jenne said.