Serology tests detect antibodies in the blood that indicate the person has been exposed to the COVID-19 virus in the past. The data, extrapolated to the general population, gives public health officials a baseline snapshot of the spread of the virus. "We calculate that there were almost 36,000 COVID-19 cases in Alberta as of May 20," she said. The numbers indicate that Alberta's testing program had identified about 17 per cent of the cases by that point, she said. show that about 12.5 per cent of estimated cases in the province had been identified up to that point.

Source: CBC News July 30, 2020 19:30 UTC