What explains this new summer wave of COVID-19? | Coronavirus

1. Where do we see this new wave?

There are currently more than 800,000 new infections per day worldwide, down from less than 500,000 in early June. Remember that during the strongest wave since the pandemic began or in January 2022, there were more than 3 million cases per day worldwide.

Several countries in Europe are struggling with a new wave. For example, Italy recorded more than 133,000 cases in one day on Tuesday and France nearly 250,000, numbers not seen since February’s surge.

Portugal, Greece, Switzerland, Austria and Australia are among the countries facing significant increases in infections.

On the other hand, the World Health Organization (WHO) warns of the small number of tests obscures the true picture of the situation.

This is especially true in Canada, where despite an almost untested population, several signs point to a summer wave. The positivity rate – which is the proportion of confirmed cases out of tests conducted – has hovered around 12% in the last week. This indicates that community transmission is high.

In Quebec, the positivity rate is nearly 15%, the same level as during the last wave. In Quebec too, the number of hospital admissions has increased by 400 in two weeks.

In Ontario, sewage analyzes show that the amount of SARS-CoV-2 in the population is increasing, a sign that a new wave has begun.

The same trends can be seen elsewhere in the country, such as in New Brunswick and Prince Edward Island.

2. Shouldn’t the virus be seasonal, like the flu?

We know that other human coronaviruses (HCoV-229E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43) show seasonal trends, with an increase usually in winter.

While some evidence suggests that SARS-CoV-2 may one day become seasonal, that is not the case yet. At the moment, new waves are more associated with the emergence of new variants.

Remember that over the past year, five interesting lines have managed to become dominant.

3. Which variants are involved?

In Europe and America, the subvariants Omicron BA.4 and BA.5 are responsible for this increase in infections. Remember that subvariants BA.1 and BA.2 were responsible for the winter and spring waves.

The BA.3 could not win.

After establishing itself in several European countries, the BA.5 is on the verge of becoming dominant in Canada and the United States.

Based on the latest available data in Canada (New window), BA.4 and BA.5 account for more than 20% of cases. In Quebec (New window)In the week of June 12, these two subvariants accounted for 34% of cases; in Ontario (New window)it was 33%.

However, it should be noted that this data is from mid-June. The proportion of cases caused by BA.4 and BA.5 would be greater than 50%.

In the United States, BA.5 accounts for about 54% of cases, while BA.4 accounts for 17% of infections.

4. Are these variants more dangerous?

Certainly each new subvariant of Omicron is more transferrable than the original strains.

The infectiousness of a disease is calculated according to the basic reproduction number (R0), ie the average number of people who become infected through a first case in a non-immunized population (vaccination or infection).

The Wuhan Tribe (Alpha (New window)) has an R0 of 3.3; delta (New window) has an R0 of 5.1; the BA.1 (Omicron (New window)) has an R0 of 9.5 and the BA.2 has an RO of about 13.3. According to a preliminary study (New window) – not peer-reviewed – it is estimated that the R0 of BA.4 and BA.5 would be around 18.6, which is similar to the contagiousness of measles.

According to the WHO, there is not yet enough data to show with certainty that BA.4 or BA.5 cause more severe disease.

In South Africa, the wave caused by these subvariants does not appear to have caused a significant increase in hospital admissions. However, such an increase can be observed in some countries such as Portugal, Italy, France and the United Kingdom.

A Japanese study (New window) (not peer reviewed) shows that BA.4 and BA.5 appear to replicate better in the lungs than BA.2 (which replicates mainly in the throat and nostrils). This suggests that these subvariants could lead to more serious complications than previous Omicron subvariants.

5. Are there other variants to consider?

In some places around the world, especially India, another Omicron subvariant, BA.2.75, is responsible for a further increase in infections. It has not been classified as an interesting variant by the WHO.

There is still little data and analysis on this subvariant, but authorities are watching it closely as it is the seat of eight more mutations than BA.2 related to the spike protein. The spikes act as receptors that allow the virus to attach itself to human cells to start an infection.

These mutations signal that BA.2.75 is at risk of escaping the immunity conferred by BA.2 infection. Thus, a person recently infected with BA.2 could be re-infected by this new subvariant.

6. Why should we avoid reinfection?

As we’ve seen since the introduction of Omicron, immunity mediated by vaccines or infection is no longer as effective. Mutations allow variants to partially escape him.

It should also be remembered that a large proportion of the population has not yet received their third dose and many people have received their last dose more than six months ago. However, studies show that the immunity provided by vaccination decreases over time and that a third dose is required, particularly in the case of Omicron.

“Omicron changed that Game ‘ said Canada’s Chief Public Health Officer, Dr. Theresa Tam, during a health committee hearing in the House of Commons in early June. According to Health Canada (New window)Individuals who received a booster dose (3rd dose) have a five times lower risk of hospitalization and a six times lower mortality rate than unvaccinated individuals.

There are also many questions about the consequences of repeated infection. According to a new American study (New window)which has not yet been peer-reviewed, repeated infection seems to increase the risk of suffering severe and sometimes long-lasting consequences of the disease.

The researchers, using data from the US Department of Veterans Affairs, were able to combine the records of around 250,000 people who were infected once with those of 38,000 who were reinfected and more than 5.3 million people who were reinfected had not been diagnosed with COVID-19.

According to their observations, those who had two or more infections were twice as likely to die from the disease and three times as likely to be hospitalized within six months of infection. Those infected also had more lung and heart problems, fatigue, digestive and kidney problems, diabetes and neurological problems.

The authors note that study group members generally have more comorbidities that may make them more vulnerable. It is therefore difficult to say whether these results will resonate in the same way in the general population.

7. How can you protect yourself?

According to the Swiss cheese model, a number of measures are necessary to contain the spread of the virus. All cheese slices – all interventions – are important. When they are placed on top of each other – through the combination of a series of interventions – the cheese is more watertight.

Photo: University of Queensland/Ian MacKay

Masks, rapid self-tests, ventilation and vaccination: André Veillette reminds us that we have all the means at our disposal to reduce the impact of this new wave. People don’t use them enoughsaid this immunologist and researcher at the Montreal Clinical Research Institute in an interview with RDI.

He recommends continuing to wear a mask in closed and crowded places like public transport and even at festivals. At an outdoor festival, if we’re less than a meter above each other, it’s like we’re indoors.

It should also be borne in mind that quick self-tests are offered in most federal states. They are considered very effective in determining whether a person – asymptomatic or not – has a high viral load and is therefore contagious at the time the test is performed. It should be noted that sometimes a person can get a positive result just a few days after the onset of symptoms similar to those of COVID-19.

According to guidelines from various health authorities in Canada, an infected person must self-isolate for at least five days. If the person has not had a fever for 24 hours afterward and their symptoms improve, they can resume activities while continuing to wear a mask. It is important to remember that many people remain contagious for up to ten days.

Regarding vaccinations, Mr. Veillette recommends that everyone – not just seniors – who had their last vaccination more than six months ago get their third or fourth vaccination. You don’t have to wait.

Leave a Comment