Strains from Europe and Eastern Canada account for most COVID-19 cases in B.C., genomic data shows

Strains traced to Europe and Eastern Canada are by far the largest source of COVID-19 infections in B.C., according to new modelling presented by the provincial government Thursday.

Provincial Health Officer Dr. Bonnie Henry revealed the results of genomic tracing of different strains of the virus, showing that of those samples that have been sequenced, early cases linked to travel from China and Iran appear to have been well contained, leading to relatively few other infections.

But beginning in March, with an outbreak that began with the Pacific Dental Conference in Vancouver, infections with strains from Eastern Canada and Europe spiked dramatically.

"One of the people that we knew was positive and had attended that conference had previously been in Germany during his incubation period before he became ill," Henry said.

Strains traced to Washington state have also been linked to a large number of cases, particularly in long-term care homes in the Vancouver Coastal Health region.

Henry explained that this kind of tracing is possible because the genome of the virus changes relatively quickly, but not as fast as diseases like influenza.

She also announced nine new confirmed cases of the virus on Thursday, for a total of 2,632 to date. No new deaths have been recorded, leaving B.C.'s total at 166.

The new cases announced Thursday include four people who have already recovered, people that Henry described as epidemiologically linked to previous patients who have tested positive.

This means these four people were close contacts of known cases and developed symptoms of COVID-19, but may not have had access to testing at the time.

There are currently 26 people in hospital, including six in intensive care. To date, 2,265 people have recovered from their illnesses, and there are now 201 active cases across the province.

Meanwhile, there has been a new community outbreak at the Beresford Warming Centre in Burnaby, where three people have tested positive for the virus.

Richmond has lowest caseload in Lower Mainland

For the first time, Henry also provided more detailed geographic data about COVID-19 cases in B.C., breaking them down by the 16 health service delivery areas.

The numbers show that in the Lower Mainland, Richmond has had the lowest percentage of cases, with just 444 per million residents, compared to 832 in Vancouver, 911 on the North Shore, and 1,241 cases per million in the area from Abbotsford to Hope in Fraser Health.

The numbers also show that Richmond had no new COVID-19 cases in the last two weeks of May, the only part of the Lower Mainland where that was the case. 

As well, 83 per cent of B.C.'s new cases in the last two weeks of May were in just two health delivery areas — Fraser East and Fraser South.  

In the rest of the province, the only sub-region with a significantly higher percentage of COVID-19 cases was north Vancouver Island (comprising areas north of Qualicum Beach), with 483 cases per million residents compared to 92 cases in central Vancouver Island and 112 cases in south Vancouver Island. 

Men account for more deaths and hospitalizations

The figures presented by Henry also show a trend that has been noted in most other parts of the world. 

While slightly more women and girls have tested positive for COVID-19 in B.C., men and boys have been much more likely to have serious cases of the disease.

About two-thirds of COVID-19 patients who have been hospitalized were male — a proportion similar to those in intensive care and those who have died.

"We've talked about the biological reasons why this might be, but we do not have all the answers yet," Henry said.

Meanwhile, people over the age of 70 are much more likely to die from the virus, even though people between the ages of 30 and 60 account for the majority of infections.

Other data presented Thursday suggest that since businesses and services began reopening on May 19, British Columbians have managed to keep their social contacts to between 30 and 40 per cent of what they were before the pandemic.

"That's what we want to see," Henry said.

She also said that modelling suggests that the partial reopening of schools that began on June 1 should have minimal impact on the spread of the virus, as long as adults maintain social distancing and those who are ill commit to self-isolating.

B.C. is now testing between 1,500 and 2,000 people for COVID-19 every day, and the percentage of those tests coming back positive has fallen in recent weeks. Anyone with symptoms can now get tested, and Henry said the province has the capacity to ramp up the testing rate if necessary.

If the curve of infection remains relatively flat, Henry said, she is hopeful that travel within B.C. will be safe by late June or early July.

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