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18/05/2022 - Covid-19

COVID-19 causes three times as many deaths as influenza in hospitalised patients in need of oxygen

A study by doctors and researchers at Hospital del Mar and the Hospital del Mar Medical Research Institute confirms that COVID-19 infection is much more virulent than the flu in this group of patients, despite the fact that they are younger and in better health. They also require longer hospital stays and more care. This means that the price of their treatment is double that of patients admitted for influenza, with an extra cost of almost 10,000 euros. The study has been published in the journal Clinical Infectious Diseases and presented at the European Congress of Microbiology and Infectious Diseases held in Lisbon.

The fact that COVID-19 is not an influenza has become clear in the more than two years of the pandemic. Despite some commonalities, it is a much more virulent disease, resulting in more hospital admissions. Now, a study by doctors and researchers at Hospital del Mar and the Hospital del Mar Medical Research Institute, published in the journal Clinical Infectious Diseases, confirms this. In the most serious patients, those who are admitted to hospital and need oxygen, mortality is three times higher among people admitted for COVID-19 compared to those admitted for the flu. Specialists from the Infectious Diseases, Radiology, Geriatrics, Internal Medicine and Pharmacy departments at Hospital del Mar all participated in this work, as did the Microbiology Department of the Catalonia Reference Laboratory.

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Thirty-day mortality among those admitted for SARS-CoV-2 infection in this situation is 15%, reaching 19% 90 days after admission. In contrast, only 5% of patients with influenza die within a month of admission, and 6% three months later. Another fact to consider is the age of the patients who have died, which was higher in those affected by COVID-19, 81 years, than in the other group, 77.5 years, verifying age as a risk factor. To reach this conclusion, 187 patients were analysed for each pathology. In the case of influenza, to attain this figure, data had to be collected for three years, 2017, 2018 and 2019. However, for COVID-19, only the first few months of the pandemic, between March and May 2020, had to be reviewed.

"COVID-19 is associated with worse clinical and economic outcomes than seasonal influenza in these patients", explains Dr Juan Pablo Horcajada, one of the authors of the study, head of the Infectious Diseases Department at Hospital del Mar and coordinator of the Infectious Pathology and Antimicrobial Research Group at the IMIM-Hospital del Mar. "Hospitalisation for COVID-19 is more complex and costly than for the flu, due to the patients' condition being more severe, the length of stay, ICU bed occupancy, the need for respiratory support equipment, and other special measures", he adds.

Younger, but more severe patients

Patients admitted for COVID-19 were generally younger than those admitted for the flu (67 years old on average compared to 76). They also had fewer comorbidities, such as hypertension, immunosuppression or chronic cardiac, respiratory or renal pathologies, which were more common in the other group analysed. On the other hand, they did have a higher rate of overweight. Most suffered from pneumonia, 98%, while among those affected by influenza, this percentage fell to 59%. "Although patients admitted for the flu were older and had more comorbidities, those admitted for COVID-19 and in need of oxygen had worse clinical and economic outcomes", says Dr. Inmaculada López Montesinos, first author of the study and consulting physician in the Infectious Diseases Department.

These individuals were also in a worse condition when they arrived at the hospital. In this sense, the stay in the intensive care unit was longer (in fact, these patients are three times more likely to end up in the ICU). They also needed to be hospitalised for longer periods of time. All of this led to higher spending on pharmaceuticals and various tests. In general, the cost of care in this group of patients is twice as high as in cases of the flu, with an average increase of 9,268 euros.

"In all respects, the results in COVID-19 patients were worse", remarks Dr. López Montesinos, who adds that "The higher mortality rate may be due to a higher intrinsic severity in this pathology, and not only to an exacerbation of the patient's chronic conditions or pneumonia." Although at present, the high vaccination rate and knowledge of the disease facilitate its management, she warns against complacency and the notion that we are dealing with a kind of influenza. "Care must be taken when 'flu-ising' COVID-19, because in a patient who is admitted in need of oxygen, it is not, it is still much worse."

The paper was presented at the European Congress on Microbiology and Infectious Diseasesorganised by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), held this April in Lisbon.

Reference article

Inmaculada López Montesinos, Itziar Arrieta-Aldea, Aitor Dicastillo, Flavio Zuccarino, Luisa Sorli, Roberto Guerri-Fernández, Isabel Arnau-Barrés, Maria Milagro Montero, Ana Siverio-Parès, Xavier Durán, Maria del Mar Arenas, Ariadna Brasé Arnau, Esperanza Cañas-Ruano, Silvia Castañeda, Ignacio Domingo Kamber, Joan Gómez-Junyent, Iván Pelegrín, Francisca Sánchez Martínez, Elena Sendra, Lucía Suaya Leiro, Judit Villar-García, Xavier Nogués, Santiago Grau, Hernando Knobel, Silvia Gomez-Zorrilla, Juan Pablo Horcajada, COVID-MAR Group, Comparison of hospitalized COVID-19 and influenza patients requiring supplemental oxygen in a cohort study: clinical impact and resource consumption, Clinical Infectious Diseases, 2022;, ciac314,

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