As COVID-19 variants spread, why are global coronavirus cases declining?

In an encouraging sign for the COVID-19 pandemic, the number of new coronavirus cases around the world and in Canada is continuing to fall this year.

For the fifth consecutive week, the World Health Organization (WHO) reported a decline in new infections on Wednesday. With a 16 per cent reduction compared to the previous week, 2.7 million new cases were documented last week, the WHO said. The number of new deaths also fell by 10 per cent.

“There has been a significant and global drop in disease week-on-week for the last four or five weeks. We haven’t seen levels as low as this as last October,” Mike Ryan, executive director of WHO’s health emergencies programme, said at a news conference on Monday.

Nationally, Canada has seen a steady drop in daily case counts, with a seven-day average of 2,886 new daily cases reported for the week of Feb. 11 to 17.

“We have reasons to be hopeful and I hope everyone is taking some comfort in the fact that we can drive transmission down … with our individual-level actions if we are enabled to do so,” Maria Van Kerkhove, WHO technical lead for COVID-19, said on Monday.

1:57 Active COVID-19 cases declining in all but one area of the province

Experts believe that a number of factors, including adherence to public health guidelines, strict lockdowns and reduced travel, are likely contributing to the downward trend in cases.

Some studies suggest that the rollout of highly effective vaccines could also be playing a role.

A new study published in the Lancet medical journal on Thursday found that among the 7,214 hospital staff in Israel who received their first dose in January, there was an 85 per cent reduction in symptomatic COVID-19 within 15 to 28 days with an overall reduction in infections, including asymptomatic cases detected by testing, of 75 per cent.

On Thursday, Dr. Howard Njoo, Canada’s deputy chief public health officer, said there are “early indications” that coronavirus vaccines are having an impact on infection rates.

More than a year into the pandemic, partial immunity among populations and the natural seasonality effect commonly seen during epidemics that show a wave-like pattern could also be slowing the spread, according to Dr. Prabhjot Singh, chief medical and scientific advisor of CV19 CheckUp and associate professor at Mount Sinai’s Icahn School of Medicine in New York.

“Oftentimes, outbreaks do follow a bell-shaped curve, meaning they infect a lot of people and then they run into problems because of immunity in less susceptible hosts, so cases go down, until more susceptible hosts are available,” said Dr. Amesh Adalja, senior scholar at Johns Hopkins Center for Health Security.

In the United States, which has by far the world’s highest case count, weekly new cases have fallen from 1.7 million at the national peak in early January to fewer than 600,000 this week, according to the COVID Tracking Project. It also noted that new cases have declined in every state.

Dr. Martin Makary, a professor at Johns Hopkins School of Medicine, argues that the country will reach herd immunity by April.

“As more and more people become infected, there are fewer people susceptible to infection,” he told Global News.

“And in most of the world, herd immunity has started to kick in.”

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According to the WHO, herd immunity is when a population can be protected from a certain infectious disease, like COVID-19, either through vaccines or immunity developed through previous infection.

“Herd immunity against COVID-19 should be achieved by protecting people through vaccination, not by exposing them to the pathogen that causes the disease,” the WHO says.

India has the second-highest number of COVID-19 infections. The Indian government has partly attributed the dramatic drop in cases to mask-wearing, which is mandatory in public in India and violations draw hefty fines in some cities.

Adalja said that if “herd immunity” is reached in a sub-population that is driving the infections, that can have “cascading benefits” on the overall cases.

2:16 Experts try to understand India’s sharp drop in COVID-19 cases

The global decline comes against the backdrop of a spread of new, more contagious variants that are rapidly overtaking the original SARS-CoV-2 virus to become the dominant strain in some countries.

In the United Kingdom, where a lockdown was imposed on Jan. 4 to combat the fast-spreading new B.1.1.7 variant, infections have dropped by more than two-thirds since last month. An interim report tracking monthly figures was released by researchers at Imperial College in London on Thursday.

Adalja said the new variants still spread in the same manner and can be blocked using the same public health measures that have been in place.

National modelling released on Friday emphasized the imminent threat of the variants, with Canadian health officials warning that the pandemic could “resurge rapidly” if public health measures are further lifted.

Recent modelling out of Quebec and Ontario also suggests that the B.1.1.7 variant, first detected in the U.K., could dominate in a matter of weeks.

2:44 Highly transmissible U.K. COVID-19 variant confirmed in all Canadian provinces

Jean-Paul Soucy, an infectious disease epidemiologist and PhD student at the University of Toronto, told Global News that once the new variants replace the old strain, Canada could see a surge in cases that could spark a third wave in the country.

But pointing to the U.K.’s example, he said the “good news” is that we can suppress the growth of the variants with “traditional measures” – lockdowns, masking, handwashing and physical distancing.

Singh said the spread of new variants raises concerns that a surge could be coming, but the decline in cases offers an opportunity to prepare for the months ahead.

“There are real drops – and it’s a chance for us to double down on what works and get ready for the potential of another surge.”

 — With files from Reuters, The Associated Press.