Why delta variants are spreading COVID-19 so fast-what does this mean for Canada


When it comes to the COVID-19 pandemic, everyone now thinks of this word: Delta.

This Highly infectious variantsIt was first detected in India at the end of 2020, has now spread to all parts of the world, and now accounts for most of the cases in Canada and various other countries.

The recent spread in the United States has led the Centers for Disease Control and Prevention (CDC) to recommend that Americans wear masks in areas where there is a large number of transmissions “regardless of vaccination status.”

So why does this particular variant spread so quickly? What is the mechanism behind its apparent success in infecting human hosts?

The answer is complicated. There are still unknowns as to how the delta variant can gain a foothold at such a fast speed and bring trouble to the global effort to contain the pandemic.

But we are getting closer and closer to understanding how it works — and why vaccines, thank goodness, are still effective.

How contagious is delta?

The delta variant is considered to be more contagious than the early strain of SARS-CoV-2, which first swept the world. Delta is called a worrying variant by the World Health Organization (WHO).

Dr. Michael Ryan, Executive Director of the WHO Health Emergencies Programme, said at a briefing on Friday: “We are fighting the same virus, but this virus has become healthier and more suitable for spreading among us humans. .”

Scientists estimate that it spreads 50% faster than the alpha variant, which is 50% more infectious than the original strain. According to Yale School of Public Health.

This means that everyone who is infected can spread the virus to more people than before, helping this variant spread quickly among the population-in those whose immune systems have not been on high alert due to previous COVID-19 infections It spreads faster among people in the state, or get vaccinated.

Watch | WHO warns that the COVID-19 delta variant is a “dangerous virus”:

The World Health Organization stated that the trajectory of COVID-19 delta variants in some countries is almost “vertical” and warned that even some vaccinated countries are at great risk due to their high contagiousness. (Willie Cunhawan/Reuters) 0:56

Why is it easier to spread?

Although the exact mechanism that makes delta more contagious is not fully understood, new research has hinted at possible reasons for its contagion.

A laboratory-based study published in the journal Cell hosts and microorganismsResearchers from Kumamoto University and the Weizmann Institute of Science have shown that mutations in the spike protein of this SARS-CoV-2 variant can evade cellular immunity and may increase its infectivity.

Raywat Deonandan, an epidemiologist at the University of Ottawa, explained that the spike protein is a key feature on the surface of the coronavirus, which allows it to enter our cells.

“It fits the receptor on our cell and then enters the cell through that receptor. The mutation changes the shape or characteristics of the spike protein to make it more suitable,” he said.

“So you need fewer viruses to achieve infection.”

On July 27th, people wear masks while walking at Grand Central Station in New York City. Due to the rapid spread of delta variants, the US Centers for Disease Control and Prevention now recommends the transmission rate of COVID-19 in fully vaccinated people. (Spencer Pratt/Getty Images)

Another study by the Chinese teamStudies that have not been peer-reviewed have found that people infected with the delta variant carry an average of more than 1,000 times more virus in their noses compared to the original strain-which may mean that they are shedding more virus.

The researchers also found that people who tested positive for this variant were faster: about four days after exposure, compared to about six days for the original strain. This shows that delta replicates faster in someone’s body.

Sharon Peacock, a microbiologist who is responsible for sequencing the genome of the British coronavirus variant, recently told Reuters: “You may actually excrete more virus, which is why it spreads more easily.”

How can the vaccine prevent it?

If carrying delta means that people may spread more viruses and spread it more easily to others, then vaccines will definitely face a more difficult task-because people’s immune systems now face a larger army and need to strengthen their defenses .

In the United States, the CDC warned on Friday that Emerging data Research from a county in Massachusetts suggests that a higher viral load may mean that people who are vaccinated can still transmit delta to others.

But the good news is that leading vaccines, including those approved for use in Canada, seem to prevent serious diseases that can lead to hospitalization or death.

A recent study in the New England Journal of Medicine It was found that two doses of Pfizer-BioNTech vaccine were 88% effective against delta variants, while the two-dose AstraZeneca-Oxford vaccine was 67% effective.

Compared with the earlier alpha variants, this marks a decrease in the vaccine’s ability to suppress infections of any severity (whether mild or more severe), but the researchers say there is only a “modest difference.”

On July 27, a healthcare provider received the Pfizer-BioNTech COVID-19 vaccine at a temporary clinic in Toronto. The leading vaccines do seem to prevent serious diseases that can lead to hospitalization or death, even for delta variants. (Evan Mitsui/CBC)

recent Data from Israel It also showed that Pfizer injections reduced the risk of serious illness by 91% and the hospitalization rate by 88%. Overall, the level of protection against symptomatic infections is less than half, but there are still questions about how the government collects data and how many infections are involved.

Nonetheless, this is a promising real-world snapshot of how leading mRNA vaccines protect against serious diseases, and the highly similar Moderna vaccine used in Canada is likely to produce similar results.

Angela Rasmussen, a virologist at the University of Saskatchewan’s Department of Vaccines, emphasized: “I don’t want to minimize the risk of’long-term COVID’, but one of the biggest risks is that you will become severely affected by the infection. How likely is the disease?” and the infectious disease organization.

“The most important thing is,” she said, “vaccination still has a strong protective effect.”

How common is delta?

Since it was first reported in India in October 2020, this variant must have become popular worldwide, and other countries have subsequently reported high levels.

Shane Crotty, a virologist at the La Jolla Institute of Immunology in San Diego, told Reuters: “It beats all other viruses in the competition because it spreads more efficiently.”

In the United States, delta now accounts for more than 80% of new infections. In many areas with low vaccination rates, cases have surged, and data shows that unvaccinated people account for nearly 97% of all severe cases.

Throughout Africa, low vaccination rates and the rise of delta variants have put tremendous pressure on hospital systems in various countries.

The WHO announced at the end of July that this variant has now been found in at least 26 African countries, and cases in 21 countries have increased by more than 20% for at least two consecutive weeks.



Countries from the UK to Singapore are also responding to delta surges—including Canada. This variant of the virus now constitutes the majority of our SARS-CoV-2 infections.

According to the latest whole-genome sequencing data from the Public Health Agency of Canada, by early July, delta accounted for about 70% of the country’s variant cases.

This marked a significant jump compared to early May, when delta still accounted for less than 10% of sequencing infections.

So what does all this mean for Canada?

There are now more and more signs that a rise in delta may trigger another surge in overall cases-although nearly 6 out of every 10 Canadians are now vaccinated, millions of people are still unprotected .

After declining for several weeks, the daily new COVID-19 cases in Ontario and Quebec have basically stabilized, while The number of new cases reported daily in B.C. has actually tripled In the past three weeks.

Viruses too Spread faster in Alberta Compared with the third wave of the province’s peak Relax the most stringent restrictions Around wearing masks and isolation requirements.

Watch | Alberta has cancelled most COVID-19 quarantine and testing requirements:

Despite the increasing number of cases in the province, Alberta will remove requirements for COVID-19 testing, contact tracing and isolation. 2:05

Even if the overall case growth starts to soar, some experts still hope that Canada as a whole can avoid the most terrible results, including the huge pressure on the country’s hospital network and the death toll similar to the previous wave.

Rasmussen said that even in densely populated urban areas, most people can still avoid infection if they are vaccinated and act safely, although she does expect an outbreak in schools if no mitigation measures are taken.

Deonandan said that many Canadians still wear masks and take precautions in social situations.

“I am quite optimistic that if such good decisions continue, we can become world leaders in this endeavour.”



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