Serology study gives officials first look at spread of COVID-19 through Alberta's population

Early efforts to flatten the COVID-19 curve were successful, according to an analysis of serology tests that has given the province a baseline to better understand the spread of coronavirus through the population, Alberta's top doctor says.

Random tests suggest swab tests identified 17 per cent of actual cases in province

Alberta chief medical officer of health Dr. Deena Hinshaw updates media on the Covid-19 situation in Edmonton. (Jason Franson/The Canadian Press)

Early efforts to flatten the COVID-19 curve were successful, according to an analysis of serology tests that has given the province a baseline to better understand the spread of coronavirus through the population, Alberta's top doctor says.

In the first week of June, laboratories analyzed almost 9,400 anonymous, random samples from blood tests collected for other clinical reasons, Dr. Deena Hinshaw, the province's chief medical officer of health, said at a new conference on Thursday.

Less than one per cent of those samples, which reflected infections that happened before the middle of May, showed the presence of antibodies, Hinshaw said.

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. "As of that date, we had identified just over 6,000 cases through swab testing."

The numbers indicate that Alberta's testing program had identified about 17 per cent of the cases by that point, she said.

"This number may sound low, but it's actually very good," said Hinshaw, who noted that serological studies in B.C. show that about 12.5 per cent of estimated cases in the province had been identified up to that point. 

Similar studies in Spain, Sweden, California, she said, suggested that between 1.3 per cent and 9.7 per cent of cases were identified using swab tests.

"Along with the data on case numbers and hospitalizations, this indicates that Alberta's early efforts to flatten the curve and limit the spread of COVID-19 were successful," Hinshaw said.

"The other thing this tells us is that as of mid-May, a very low percentage of our population had been infected with COVID-19."

The analysis conducted in June will be repeated each month to further track the spread.

Latest numbers

The province reported five more COVID-19 deaths on Thursday and 113 new cases of the illness.

As of Thursday, there were 1,408 active cases in the province, with 91 people being treated in hospital, 18 of them in ICU beds

The deaths reported Thursday by Alberta Health were all residents at the Good Samaritan Southgate Care Centre in Edmonton.

Some of those deaths had already been reported by the facility itself.

The centre is battling an outbreak of the disease that has now killed 21 residents and sickened dozens more.

On Thursday, the centre had 54 active cases among residents and 16 among staff members.

The Good Samaritan Southgate Care Centre in Edmonton has reported 21 deaths due to COVID-19. (Scott Neufeld/CBC)

There are about 180 residents in the facility, at 4225 107th St.

All outdoor visits have been cancelled, additional cleaning staff have been brought in, and the centre now screens employees and residents twice a day.

Alberta Health Services considered taking over day-to-day operations of the centre last week, but decided the move was not necessary, Tom McMillan, assistant director of communications for Alberta Health, said Monday in a statement.

AHS is working with the centre to provide oversight and leadership and ensure that all processes and procedures are up to standard, including securing necessary staff, McMillan said.

Expanding pharmacy testing

Hinshaw also announced Thursday that Alberta is expanding testing at community pharmacies.

Any pharmacy that wants to participate and can meet the safety requirements will be allowed to offer tests to people who have no symptoms and no known exposure to COVID-19.

Under a pilot program launched in June, an initial group of pharmacies tested more than 10,300 people, Hinshaw said.

This pilot was kept small to allow the province to refine the process.

"Based on this success, we are expanding this program to any pharmacy that wants to offer testing and is able to meet the safety requirements.

Testing can begin as soon as the pharmacy is enrolled and receives the necessary supplies, said Hinshaw, who urged people to be patient as it will take time for pharmacies to enrol and get the necessary supplies.

There are currently 94 pharmacies enrolled in the program across the province, with 16 in Edmonton and 40 in Calgary.

A list of pharmacies will be available on the Blue Cross website and will be updated frequently, she said. People are encouraged to call the pharmacy to find out whether they need to book an appointment.


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