B.C. holding on to contact tracing strategy, though it’s at risk

B.C. health officials committed early on to a COVID-19 strategy that consisted of testing, contact tracing and isolation and so far it's holding up – but barely.

The number of COVID-19 cases where the source of exposure is unknown has started to rise, and Dr. Bonnie Henry said the strategy is "on the edge."

So far, only 20 to 25 per cent of cases can't be traced back to a source — that's been consistent for a while — but the Fraser Health area has been an issue.

"Fraser (Health) has been the most challenging area. because we've had such a rapid increase (of cases) in a short period of time, but most of the cases are definitely linked," she said,

Another challenge has been tracing the disease fast enough to stop it before it's been passed on.

"That's where we're trying to catch up but we are still very much committed to our contact tracing approach, and it is still within our grasp, though, as I've mentioned, last week in particular, it was getting very, very close," Dr. Henry said, adding later that some of her colleagues have had to abandon the strategy in other places in the country.

To highlight the changes in contact tracing since the start of the pandemic, the BC CDC Situation Report issued on Nov. 20 indicated that local contact with a known case or cluster has most often been considered the source of infection across all pandemic phases to date.

"Prior to  Phase  1,  international  travel  was  also a frequently  cited  source  of  SARS-CoV-2  infection in  part  reflecting high risk testing that targeted returning travellers. However, travel-related restrictions introduced in Phase 1 limited that contribution thereafter with clusters, such as in care facility settings, becoming a more prominent source," the report reads.

"Since around mid-Phase 3a more cases have cited unknown local exposure or that information remained pending or missing. International  travel  has  been  cited  less  often  since  Phase  3b  and  these  patterns  have  been  generally  maintained  through week 46."

Helping keep the strategy on track is the summer commitment to hiring 500 contact tracing supports for public health — that's well on its way to being done.

"It's always a challenge to get things in place in time," Dr. Henry said.

As for whether the plan is working well enough, Dr. Henry said it was too early to say.

"You know, there are so many things so I don't think we're at the point where we can say we should have done one thing or another thing — we've tried a whole bunch of things," she said. "I will say that I was surprised at how soon in the fall we started to see the surge."

Looking at the numbers, they show that they went from around 100 cases a day and gradually went up in September.

"Then we had an explosive growth in the Lower Mainland and now we're seeing that that's spreading around to other parts of the province," she said. "So the orders I brought in last Thursday (are an attempt at) trying to get ahead in all the other parts of our province, not (getting) behind like we were a bit in Fraser Health."

Those orders involved curtailing social gatherings.

Whether it worked remains to be seen. Interior Health has continued to see a rise in cases and had 70 yesterday, for a total of 1,426.

Currently, 336 cases are active and in isolation in the health region that covers the Southern Interior, while five people are in hospital.

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