"In September 1918, it came mainly from soldiers and it was a virus that affected young adults, there was a very sharp peak at 28 years old," explains Alain Gagnon, professor of demography at the University of Montreal and specialist in pandemics caused by influenza.
As for the pandemic of 2009, the school environment had acted as a place of "amplification of the virus", according to the epidemiological assessment of the National Institute of Public Health of Quebec (INSPQ).
What the two pandemics have in common: the two viruses were of the H1N1 type.
The coronavirus is different. "The risk of being infected seems to be lower in children, but there are many questions about their role of transmission, it is a group for which we are in a very unusual situation", explains Gaston De Serres, epidemiologist at the INSPQ.
In addition, in 2009, the cities of Montreal and Laval were affected during the first wave, then the following fall it was the turn of the regions.
This time, even if Montreal has more cases, we do not know the percentage of people infected. "Maybe it's only a small percentage infected," believes Dr. De Serres. So there is little chance that the immunity that played in 2009 in Montreal will occur this time. "
Mutation of the virus
A second wave can occur when the virus mutates. "We know that for the Spanish flu it was an H1N1, but had the virus undergone a significant mutation in September? It remains a mystery, ”says Mr. Gagnon.
"For coronaviruses, some say that mutations are less common, but since we have never tested this one, so we remain cautious," added the demographer.
A second wave could also occur if COVID-19 is seasonal like H1N1. “For the other coronaviruses, there is a seasonality. These are viruses that give colds and are transmitted more in winter than in summer, but for this new virus we do not have the answer ", says Nicholas Brousseau, medical consultant at the INSPQ and co-author of the assessment from 2009.
"Perhaps the weather conditions during the summer will be less favorable, but to think that it would be enough to reduce the epidemic, the hopes are very slim", continues Dr. De Serres.
Focus on distancing
Thus, public health does not rely on Mother Nature to curb the pandemic and avoid a second wave, but rather on social distancing, insists Dr. De Serre.
D r Brousseau recalls that in 2009, there was no containment measure to curb the spread of H1N1.
“This year, the distancing measures have an important impact to avoid several hospitalizations and deaths. The question is to find the balance to return as much as possible to normal life without significant resurgence of the infection. "
