COVID’s R-Value (or Spread Capacity) Rises Again in Alberta

The average number of COVID-19 infections transmitted by each diagnosed case is on the rise again in Alberta.

Over the past two weeks, the province-wide R-value of Alberta was 0.84, with a confidence interval of 0.74 to 0.94. It was even higher in Edmonton, at 0.97, with a confidence interval potentially pushing the city’s R-value above one.

The R-value represents the number of people infected by each infected person.

These numbers are up from previous weeks when the R-value was 0.75.

The question is whether we are going to see in Alberta what is happening in the United States and what is happening in the United Kingdom.– Dr Chris Mody

Dr Chris Mody, head of microbiology, immunology and infectious diseases at the University of Calgary, says that while it is good that cases are on the decline, the R-value (or reproduction value) shows as the rate of decline in cases reaches a plateau.

“At the moment, we are doing very well,” he said, adding that the province is unlikely to see the impacts of the reduced public health restrictions until early August.

“What becomes a problem is if that R-value goes up to one and then starts to increase – and we don’t know the answer to that in terms of how lowering restrictions will affect that R-value.”

Mody said it’s important that the R-value stay less than one.

At an R-value of one, each person with COVID-19 transmits it to only one other person. If this number is greater than one, the number of cases increases. But once it drops below one, it means the cases go down.

For COVID-19, research suggests the R-value averages around 2.6 to 2.7 with no intervention in place – like masks or physical distancing – meaning that if left unchecked, it could spread exponentially.

The R-value therefore depends not only on the degree of contagion of the coronavirus, but also on the effectiveness of the company in preventing it from spreading.

“We know that no matter what we do to change things, these cases are a few weeks late. So if you think about the day when [Calgary] The Stampede ends, you know, then the effect will be two weeks later, ”Mody said.

Vaccinations will be essential to stop this spread, he added.

“The question is whether we are going to see in Alberta what is happening in the United States and what has happened in the United Kingdom. And this is based on the delta variant causing infections primarily, but not exclusively… in unvaccinated people. And that’s where the risk lies. “

The delta variant is more transmissible and has caused an upsurge in new cases in areas like the UK. There were 906 cases of the delta variant in Alberta; 351 of the province’s 599 total active cases are variants.

Nearly half of Alberta’s population has been fully vaccinated against COVID-19.

Trevor Tombe, professor of economics at the University of Calgary, said where the province lags behind is in the share of the population who received a first injection.

“Other provinces have a much larger portion of their populations that received this first injection. So it could be that Alberta and Saskatchewan have a much more difficult challenge in terms of vaccine hesitancy and that is really going to weigh on the next two weeks, “he said.

Projections from Tombe show that Ontario will have 80 percent of its population vaccinated with at least one injection by the end of July, while Alberta will be lower at 75 percent.


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