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While the number of COVID-19 cases is breaking all records in Quebec, the death rate among those affected remains much lower than during the spring surge. Will researchers understand the causes in time to allow the trend to continue?
Since the beginning of autumn, through the daily deluge of statistics on the pandemic, one element seems to contradict the gravity of the situation: the death rate of the case, or the percentage of infected people who die from the disease. COVID-19.
Although the number of cases is soaring, mortality from the disease has dropped dramatically since last spring – initially around 10 percent, this rate has now plummeted to nearly 1 percent, according to an Institute report. National de la santé publique du Québec (INSPQ) published in early November.
This effect goes far beyond the borders of Quebec. In the United States, the country with the highest number of COVID-19 cases, there is also a significant drop in the death rate from the disease. The same is true in England, where, over the same period, the rate dropped from 40% to 10% among people in intensive care.
At first glance, this decline seems like excellent news. But before we rejoice, it is important to understand the cause of this decline.
This remains difficult to pin down, according to Erin Strumpf, a professor in the department of epidemiology, biostatistics and occupational health at McGill University. “To understand the evolution of a mortality rate, very precise information on the population studied is needed, a precision that current data does not reach. Currently, we are comparing people who were sick last spring with those who are sick now. But these are two very different groups of people! They are not the same age or the same health profile. Even among subgroups such as hospitalized people, differences in admission criteria may be enough to produce a drop in numbers that doesn’t really reflect reality. “
Dilution effect?
Could this decrease result from a dilution effect? After all, far more people are getting the diagnostic test than eight months ago. Among them, there are many mild cases that we would not have noticed during the first wave. These younger people who will face the disease without complications “dilute” the number of serious and potentially fatal cases, which decreases their statistical burden.
However, looking at the data, we see that this decrease hides more than just an increase in the number of young or tested. “We observe this drop in mortality in all categories that we found interesting,” explains Dr. Rodica Gilca, medical consultant at INSPQ and one of the authors of the report published last November. Therefore, even the most vulnerable now appear to be less at risk of dying from COVID-19 than last spring.
Mortality from the disease was 40% in people in CHSLD between February and June, Dr. Gilca informs. Between July and September it dropped to 24%. The same is true for people aged 60 and over, the age group most at risk of dying from infection. In these people, case mortality was 27% last spring and has since dropped to 8.7%. As for hospitalized people, even if the decline is less significant, it remains significant: 27.8% last spring against 17.6% today.
“These figures suggest that the decline in the death rate among people with the disease is very real,” confirms biostatistician Erin Strumpf, “but they also raise many questions. It would be interesting to understand the cause, but for now the data limit us to hypotheses. “
Better care
For Dr.Gilca, one of the most realistic hypotheses is also one of the simplest: we now know better how to treat COVID-19, as well as better protect and isolate vulnerable people.
An improvement confirmed by Dr. Mathieu Simon, head of intensive care at the Quebec University Institute of Cardiology and Pulmonology. “We really understand better how to treat patients,” explains the doctor. Initially, invasive ventilation was performed very early, a practice that increases the patient’s vulnerability and is already associated with some mortality. We are now much less intrusive in our approach and achieve a better survival rate. “
Add to this that although there is no cure for COVID-19 yet, there are several drugs that can help severely affected patients. “Medicines like Decadron [aussi appelé dexamethasone, un anti-inflammatoire stéroïdien] greatly reduce symptoms, adds Dr. Simon. The risk of blood clots is also addressed with antithrombotic drugs. At the same time, the use of unnecessary or even dangerous drugs, such as remdesevir or hydroxychloroquine, was stopped. This series of measures may explain the decrease in mortality observed in the ICU. “
However, will this progress be enough to keep mortality at 1% if the number of cases continues to rise and this clogs up the health system? Although it is impossible to predict the future, new data from the INSPQ show that the trend continues, despite the increase in cases in the fall. “We did a follow-up study,” adds Dr. Gilca, “and although the results are preliminary, we see that case mortality remains low, despite the increase in cases in recent weeks. “
But nothing is won. “The death rate remains higher among the elderly,” adds Dr. Simon. As holidays approach and the prevalence of the disease among young people, mortality can increase among vulnerable people. “
We must also add that although the disease now seems less fatal, it is not without consequences. Many of those who have contracted it have had long-term health problems. Pending vaccines, prevention and health measures therefore remain essential.
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