What's behind the drop in COVID-19 cases in Canada and other parts of the world?

Why are global COVID-19 cases dropping? Infectious disease specialist Dr. Isaac Bogoch shares a few potential reasons for the drop in new infections.

TORONTO — Canada is experiencing a drop in new COVID-19 cases, which is mirrored in countries like the U.S. and India, and experts are trying to understand the exact reasons behind the downward trend.

According to CTV News’ COVID-19 tracker, 7,137 new cases were reported on Jan. 3. Compare that with Wednesday’s numbers – 2,606 new cases – and the drop seems stark.

Ontario, which has been in a state of lockdown for several weeks, logged fewer than 900 new cases Wednesday, numbers that have not been seen since October 2020.

With vaccine supply chains disrupted and several provinces’ rollout plans faltering, scientists have been attempting to decode the downward trend.

Toronto infectious disease specialist Dr. Isaac Bogoch says the drop in cases can be attributed to many things, but especially Canadians’ good behaviour – including abiding by lockdown rules.

“No one likes lockdowns, they’re terrible and devastating, but they work,” Bogoch said on CTV’s Your Morning Thursday. “If you have a lot of cases in an area with a lot of people and you lock it down you are going to see cases go down and we see this time and time again.”

Bogoch said other measures, such as people wearing masks indoors, are “extremely helpful” in bringing new cases down but we “can’t discount the seasonality” of COVID-19 being a factor in fewer virus transmissions.

“We still don’t know enough about it, but that may be a factor,” he said.

In the United States, records were shattered in early January for daily new COVID-19 infections, hospitalizations and deaths – right on the heels of holiday travel. But since then, new cases and hospitalization rates have plummeted and doctors in that country also partially attribute that trend to good pandemic behaviour and some evidence of what one expert called “population immunity.”

“One, we came off of really high numbers from the holidays," said Dr. Ashish Jha, dean of the Brown University School of Public Health, told CNN.

"Second, there is pretty good evidence that people are doing a better job of social distancing and mask wearing. Third, I think in a lot of communities, we've had so much infection that you have some level of population immunity. Not herd immunity, but enough population immunity that it is causing the virus to slow down."

India has also reported a dramatic fall in new cases, down from a peak of nearly 100,000 a day to 11,000 a day – which has left some experts stumped.

Bogoch said a lot of the same public health measures are at play there.

“Masks are widely used in India, and in fact there are fines if you don’t wear a mask,” he said. “So I think there are a lot of public health measures being used there.”

Bogoch also pointed out that as the virus has swept through many areas of India, especially in lower socio-economic communities, there may be “pockets of herd immunity.”

“Not the whole country, but pockets of immunity within the country because so many people have been infected with this virus - we have that data from serology studies,” he said, adding once again that experts can’t discount the concept of seasonality.

While the World Health Organization said in its latest update that the number of global COVID-19 infections has fallen by 16 per cent in one week – resulting in half a million fewer cases reported – some parts of the world, including Europe, are still very much in the grip of the pandemic due to the spread of coronavirus variants.

News of the U.K. starting human challenge trials – in which researchers intentionally give participants COVID-19 to study the virus - have been making waves. But Bogoch said he is wary of embarking on that scientific process at the moment.

“We don’t have a cure. We have treatments which are fine but no cure,” he explained. “We know that younger people who are included in clinical trials are unlikely to die because they’re young, but people are still getting pretty sick – and in addition we know there are long-term symptoms from this virus.”

Bogoch pointed out that vaccines are already being updated without human trials, so he was not “entirely sure” why the clinical trials are ongoing.

“You can get some interesting answers from them, like how much virus it actually takes to infect someone - so there is some amazing data you can glean from clinical trials, but I don’t think I am a fan of human trials for COVID-19 until there are good cures available,” he said.

Bogoch warned that even with the positive news of the number of new daily cases dropping, Canada and other countries need to approach the next few months with caution, especially due to variants.

“We have to respect the variants of concern, we don’t know enough about them, we know that some are more transmissible – we saw one COVID-19 mutation get married to another COVID-19 mutation – we still don’t know how that will work, that’s the recombinant virus,” he said. “While we have to be open-minded to new data, as things are reopening we need to approach with caution so we don’t get a third wave.”

--------

With files from CNN