What does the teachers’ strike mean for germs…

Overall, it’s “reasonable,” notes Dr. Guy Boivin, a physician and infectious disease researcher at Laval University who specializes in respiratory viruses. “I don’t think strikes will stop the pandemics that are already underway, because we’re in the middle of them right now: there’s a triple wave of influenza, Covid-19 and respiratory syncytial virus. [un des virus qui donnent le rhume, ndlr]. Don’t worry about the circulation of the virus, but it can also transmit or retard the viral pics that if the children stay in the house or don’t see anything else, they have a few contacts if they are there. At school.”

However, it is difficult to measure exactly how big a role schools play in the outbreak. There are always a lot of different things happening in a given society and we cannot separate reality into two parallel universes where the only difference is the closing/opening of schools.

During the COVID-19 pandemic, school closures were usually just one measure among many — mandatory mask-wearing, bans on gatherings, etc. – It is impossible to distinguish between the effect of each. It also often happens that schools close so late, as we approach the peak of transmission, that we cannot say with certainty whether the decline that follows is explained by the fact that students are staying home or would have happened anyway. This is without taking into account that the impact can vary from one social and cultural context to another.

In the event of the indefinite strike initiated by the Independent Education Union three weeks ago, it would be very smart to see even the slightest impact on public health statistics. The chart below shows the proportion of tests conducted in Quebec that turned out positive for influenza – one of the main indicators for monitoring influenza epidemics – and there is nothing to suggest that the strike that began during Week 47 slowed the progress.

The fact that the indefinite strike affects only slightly less than a third of Quebec students, and that other strikes have been very limited in time, no doubt masks its impact in the overall numbers.

Studies agree

However, there are still quite a few studies that have observed a decrease in cases of respiratory infections when schools stop their activities for one reason or another. One example that closely matches the current situation in Quebec is A Article published in 2004 In the Journal of Pediatric Infectious Diseases After a two-week strike by primary school teachers in Israel in January 2000. Compared to the previous two weeks, the number of respiratory infection diagnoses decreased by 42% during the strike, the number of doctor or emergency room visits decreased by 28%, and the number of medications purchased decreased by 35%

As someone pointed out Literary magazine Published in Lancet – Infectious diseases Later, during the 2009 “swine flu” epidemic, the annual influenza epidemic (which began 3-4 weeks earlier) likely would have peaked near the start of the strike, which would have magnified the effects. Returning to the classroom strongly suggests that school closures have slowed the spread of the disease.

Several other works I came to similar conclusions. The effects are not always astonishing – for example, a French study compared the impact of winter holidays, which do not occur simultaneously everywhere in France, and found a decline of about 15% in total cases, but still by 40% during peak periods – but most agree. , at least for influenza.

Exception for Covid?

It should be noted that studies conducted on this topic during the Covid-19 pandemic often produced contradictory results. Some work conclude that No effect On the transmission of the SARS-CoV-2 virus during Others noticed Efficiency up to 60%. This lack of clarity can be explained by the fact that many other health measures imposed during the pandemic may have, in some way, “swamped” the impact of school closures. It is also possible that the studies overestimated the effect by applying models developed for viruses that have been circulating for a long time, such as influenza, and to which the population is already largely immune.

Another hypothesis, The researchers arguedHe wants children to be less susceptible to infection with SARS-CoV-2 – after all, the cellular receptor that the virus attaches to, called ACE2, is less present in children. Therefore, keeping them out of schools to slow the transmission of the virus, which does not spread well among them, would not have achieved much. But it is a controversial idea because the decision to get tested is largely linked to the appearance of symptoms, which are specifically less strong, and often absent, in younger people. So we may have missed more pediatric cases, which would have created the illusion of poor transmission among children.

Regardless, Dr. Boivin says, the general rule that closing schools slows the spread of disease should apply in principle to almost all respiratory viruses. “I have not seen any convincing studies that would show differences in the way respiratory viruses spread, that would prove that one could be transmitted more by droplets, and another by aerosols.” [des micro-gouttelettes qui peuvent rester suspendues longtemps dans les airs et parcourir de plus grandes distances que les gouttelettes plus grossières, ndlr] Or via surfaces, he says. In general, it can be said that respiratory viruses generally spread in the same way, and the dominant mode is droplets emitted during coughing. As for aerosols, it remains a poorly described situation and we believe it will be less important than droplets.

Finally, let us mention that it is clear that besides the transmission of germs, school closures can have many other consequences for children (and parents), especially if they are prolonged. Delays in learning are of course among the main causes, and they mainly affect, unfortunately, the most disadvantaged young people and/or those who have already faced academic difficulties. But wait, that’s another question that goes beyond the topic of this column…

* * * * *

Do you have questions about the world around you? Whether it’s physics, biology or any other discipline, our journalist will be happy to answer it. In our view, there is no “dumb question”, and no question is “too small to be interesting”! So write to us at: [email protected].

Please note that this column will be on hiatus over the holidays. But don’t miss the 5 most important scientific discoveries made in the Quebec region, which will appear between Christmas and New Year. Back in January!