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LExperts from the National Institute of Public Health of Quebec (INSPQ) unveiled their new model of the pandemic on Thursday, presenting two scenarios, one where people respect protective measures such as physical distancing or restricted gatherings and another where the population shows a relaxation.

Although the situation in Greater Montreal is more critical, Dr. Gaston De Serres, epidemiologist at the INSPQ, underlines that the rule applies everywhere in the same way: “The less people adhere to precautionary measures, the more transmission. is able to ascend, even in poorly affected areas. If there is virus left and people are not careful, the virus will find ways to spread it. “

“Even in the regions, if people follow the precautions well, we don’t expect a comeback. If, on the contrary, they let their guard down by telling themselves that there are few cases, we can afford to have a freer life, things will go badly ”, he added during a session. technical information on the new models of the INSPQ.

Travelers: be “even stricter”

This did not prevent the researcher from issuing a more severe warning to travelers – particularly Montrealers – who will be tempted to go sightseeing in other regions.

“If there is one message that must be clear, it is that people who want to go to other regions must be even more strict in their maintenance of precautionary measures so as not to risk scattering the virus in regions which are currently spared. “

The researchers refused to give prediction figures on the number of deaths or hospitalizations in their two scenarios, which affect Greater Montreal. Both scenarios include a wide range of possibilities, but the median of these possibilities can at least be used as an indicator.

Thus, in the scenario where people would show strong support for public health measures, the number of hospitalizations would gradually decrease to around 30 per day in August and the number of deaths would increase to around 15 per day. In a scenario of non-compliance with the instructions, the number of daily hospitalizations and deaths would start growing exponentially, reaching approximately 200 and 45 per day, respectively, depending on the median. However, these medians by no means reflect the best and worst assumptions of these scenarios by far, hence the reluctance of researchers to present them as more robust assumptions than others.

Montreal succeeded in realizing the optimistic scenario

Despite everything, experts note that the situation in Greater Montreal, epicenter of the pandemic, has evolved following the optimistic scenario of their latest models, on May 7.

This optimistic scenario predicted a reduction in the number of hospitalizations if the population reduced their contacts by 60%, while the pessimistic scenario showed continued growth in hospitalizations and deaths. However, studies have shown reductions in contact from 60% to 63% and, in addition, their scenarios were based on a reopening of businesses a week earlier, as announced at that time by the Legault government, and a reopening. schools, which was subsequently postponed until next September.

“Fortunately, we are in the optimistic situation and hence the difference between our predictions now and a few weeks ago,” said Professor Marc Brisson, of Université Laval, director of the Research Group in mathematical modeling and health economics related to infectious diseases.

Next: it’s all about contacts

Their work shows that before the pandemic, a person had an average of 12.2 contacts with another person per day, with one contact defined as a conversation within two meters or physical contact such as shaking hands or kissing each other. kiss. During the maximum period of containment, the number of such contacts dropped to an average of 4.5 people per day, which includes contacts at home, at work and in shops.

In an ideal scenario, where each person would maintain exactly the same instructions, the progressive deconfinement would make it possible to maintain this number of contacts at 4.5 per day since a good part of the new contacts allowed could be made while respecting the two meters distance and other protective measures such as plexiglass on the market or masks.

This 100% adherence is unrealistic, however, but the researchers argue that the pandemic has changed behavior to the point where even with 0% adherence by one person, protective measures for others would reduce however, that average number of 8 contacts per day and 50% membership would translate to an average of 6.5 contacts per day.

These models, however, remain fragile and imperfect. The researchers note, for example, that we do not yet know the seasonality of the coronavirus, in particular its transmission rate in summer, and stress that their models, developed with data up to May 26, do not take into account the movement between regions. In addition, the document adds that they “are sensitive to the uncertainty around the behavior of distancing during the return to work and to school, and to self-deconfinement”, that is to say the non-compliance by some individuals of the rules surrounding gatherings.

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