B.C.'s COVID-19 pandemic spread largely because of virus strains from Europe, Eastern Canada, and Washington state

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      B.C.'s provincial health officer has shown that visitors from China are not the main cause of a public-health problem that has caused widespread economic hardship.

      In presentation touching on epidemiology and genomics, Dr. Bonnie Henry demonstrated that the primary source of COVID-19 infections in B.C. came from travellers from Europe, Eastern Canada, and Washington state.

      She showed this with a series of charts featuring different colours. They represented strains of the virus from different regions.

      The first positive test results for COVID-19 in B.C. in January revealed a strain similar to the one in Wuhan, China. 

      According to Henry, this wasn't a surprise because those with the disease had travelled from that region.

      However, in early February, a new strain showed up—something that Henry described as a "sentinel event" or an "indicator event".

      "We identified a person who had not travelled anywhere near China, who had come back from Iran," she said. "The testing at the time showed that she did have COVID-19. This was before Iran had notified the World Health Organization and [before] people were aware the outbreak was happening there."

      Henry revealed that this new strain could be detected through genomic sequencing conducted in B.C.

      That helped B.C. public-health officials determine that this virus was different from the ones coming from China.

      These colours represent the different genetic strains of the COVID-19 virus that have been detected in B.C.

      Moreover, the virus strain from people travelling from China was not spreading in the community because people were self-isolating.

      "So we saw this new genome sequence come in," Henry said. "And it turned out to be very highly correlated with the genome sequences that were circulating in Iran once we had that information as well."

      The next cases that popped up were what she described as "European-like and Eastern Canada". They surfaced at a large dental conference in Vancouver in early March.

      One of those who tested positive had been in Germany during the incubation phase, when he didn't become ill. 

      Henry noted that health officials found three slightly different strains of COVID-19 among people at the conference, suggesting that several people were likely ill when they attended.

      This event led to at least 87 cases of COVID-19 in B.C.

      Then there were the cases of a virus strain that could be traced to Washington state. They began a steady and rapid rise around March 10.

      "That really reflected people coming in from Washington state or us going back and forth across the border and bringing the virus back," Henry said.

      This strain was "seeding outbreaks in our community and in our long-term care homes".

      By imposing restrictions on large gatherings on March, B.C. managed to sharply drive down the number of contacts that infected people.

      The chart below shows that prior to March 15, each person who tested positive with COVID-19 came in contact with 10.7 people.

      After March 15, that fell to 3.6 people.

      Henry emphasized that these figures do not include concentrated community outbreaks at long-term care homes and in certain workplaces.

      "After we put in the restrictions and people stopped having much larger groups and gatherings, we had a third of the contacts," Henry said. "And this is how we broke the chains of transmission in British Columbia—by reducing the numbers of people that we had close contact with. And not giving the virus a chance to move to large numbers of people."

      She praised public-health teams for reaching a high percentage of those contacts in a very short period of time.

      And that, in her view, is what "helped us break the curve".

      Henry also showed that as the number of contacts rises, it will likely lead to more COVID-19 cases.

      The chart below shows by how much.

      B.C. reported only five new positive test results over the past 24 hours and none in the Vancouver Island, Northern, or Interior health regions.

      In addition, the province has identified four more cases that were "epidemiologically linked" to other cases. All four people have since recovered.

      B.C. is faring exceptionally well in comparison to other jurisdictions, as the chart below shows.

      B.C. also reported no fatalities from COVID-19 over the past 24 hours.

      There are currently six active outbreaks in health-care facilities, all in long-term care homes.

      There's also one new community outbreak at the Beresford Warming Centre in Burnaby. Henry said there are three confirmed cases there.

      The number of new cases has been kept down, in part, because British Columbians are reducing their contacts with other people.

      There are 26 people with COVID-19 in hospital, including six in critical care or an intensive-care ward.

      No new deaths were recorded over the past 24 hours.

      Below, you can see other slides presented by Henry at today's presentation.