COVID-19’s Mortality Risk 3.5 Times Greater Than the Flu
A recent study published by the Canadian Medical Association Journal (CMAJ) found that the risk of death from COVID-19 was 3.5 times higher than from the seasonal flu.
"We can now say that COVID-19 is much more severe than seasonal influenza," said Dr. Amol Verma, St. Michael's Hospital, Unity Health Toronto, and the University of Toronto, in a press statement.
Patients admitted to hospital in Ontario, Canada with COVID-19 had a 3.5 times greater risk of death, 1.5 times greater use of the ICU, and 1.5 times longer hospital stays than patients admitted with influenza during the 2019-2020 flu season.
This new study compared hospitalizations for influenza between November 1, 2019, and June 30, 2020, in 7 large hospitals in Toronto and Mississauga. There were 783 hospitalizations for influenza in 763 unique patients than 1027 hospitalizations for COVID-19 in 972 individual patients (representing 23.5% of all hospitalizations for COVID-19 in Ontario during the study period).
Most patients hospitalized with COVID-19 had few other illnesses, and 21% were younger than 50 years of age. People younger than 50 also accounted for almost 1 in 4 (24%) admissions to the ICU.
People hospitalized for COVID-19 had more significant use of the ICU, were more likely to be put on a ventilator, and had more extended hospital stays than people with influenza.
Compared with patients with the flu, patients with COVID-19 were more likely to be male and reside in long-term care, consistent with evidence that COVID-19 affects men more severely in Ontario.
These findings are similar to recent study results reported in France and the United States.
"Many people believe that COVID-19 mainly affects older people," says Dr. Verma. "It is true that COVID-19 affects older adults most severely.”
“We found that among adults over 75 years who were hospitalized with COVID-19, nearly 40% died in hospital.”
“But it can also cause very serious illness in younger adults. Adults under 50 accounted for 20% of all COVID-19 hospitalizations in the first wave of the pandemic.”
“Nearly 1 in 3 adults younger than 50 hospitalized with COVID-19 required intensive care, and nearly 1 in 10 required unplanned readmission to hospital after discharge."
Furthermore, the most responsible discharge diagnoses were attributed to COVID-19, viral pneumonia, sepsis, or palliative care in 89.7% of patients who died with COVID-19, suggesting that most of these deaths are likely attributable to COVID-19.
"These differences may be magnified by low levels of immunity to the novel coronavirus compared with seasonal influenza, which results from past infections and vaccination," says Dr. Verma.
"Hopefully, the severity of COVID-19 will decrease over time as people are vaccinated against the virus, and more effective treatments are identified. There is, unfortunately, also the possibility that variants of the virus could be even more severe."
According to recent data published by the World Health Organization, had this study been based on the 2020 - 2021 flu season, the COVID-19 mortality percentage would have been more significant.
As of February 1, 2021, despite continued or even increased testing for influenza in some countries, influenza activity remained at lower levels than expected for this time of the year. In the Northern Hemisphere’s temperate zone, including Canada, influenza activity remained below baseline, though sporadic detections of influenza A and B viruses were reported in some countries.
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