Newswise — Nov. 13, 2020─ A new study published online in the Annals of the American Thoracic Society reveals how patients hospitalized with severe COVID-19 fared, compared to those hospitalized with severe seasonal influenza. The study is believed to be the first in the U.S. to directly compare clinical features, laboratory results and health outcomes between patients with the two diseases.
In “Comparison of Clinical Features and Outcomes in Critically Ill Patients Hospitalized With COVID-19 Versus Influenza,” Natalie L. Cobb, MD, MPH, of the Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, and co-authors looked at the medical records of 65 patients critically ill with COVID-19 and 74 with severe influenza A or B who were admitted to the intensive care units (ICUs) of two UW Medicine academic medical centers between Jan. 1, 2019 and April 15, 2020. This research was conducted as a retrospective cohort study—one that follows former patients who had common characteristics.
A key finding of the study was that COVID-19 patients had in-hospital death rates of 40 percent versus 19 percent for influenza patients. This higher mortality rate was independent of the patients’ age, gender, co-occurring health conditions (comorbidities) and severity of illness while in the ICU.
Patients with both diseases frequently required mechanical ventilation. Compared to those with influenza, however, ICU patients with COVID-19 needed to remain on mechanical ventilation longer and had worse lung functioning overall. Patients with COVID were also more likely to develop acute respiratory distress syndrome (ARDS), a life-threatening illness in which the lungs become severely inflamed.
“The finding that ARDS may be more prevalent among critically ill patients with COVID is important in understanding why there may be a mortality difference between the two diseases,” said Dr. Cobb. “We also found that patients with ARDS due to COVID-19 had a trend toward worse clinical outcomes than ARDS patients with influenza.”
The researchers looked at various characteristics of patients in the two groups. COVID-19 patients had slower improvements in blood oxygen levels, longer durations of mechanical ventilation and lower rates of extubation (removal of breathing tubes) than the influenza patients. Patients with COVID-19 were also more likely to be male, have higher body mass index (BMI) and higher rates of chronic kidney disease and diabetes.
Nearly four times as many COVID patients identified as Hispanic as did influenza patients. The authors suggest that this difference may be related to underlying health factors as well as social and economic inequalities.
Dr. Cobb and colleagues noted that, early in the COVID outbreak, many comparisons were made between infection with COVID-19 and influenza, which is responsible for a significant number of hospitalizations and deaths, both in the U.S. and globally. While previous studies did not directly compare COVID and influenza, research has shown that there are important differences between the diseases in the proportion of individuals who develop severe illness and mortality.
As the flu season nears and it is likely that the nation is seeing the start of a second, or possibly third, surge in COVID cases, Dr. Cobb believes that the study’s findings present real-world public health implications.
“With rising cases of COVID-19 and the coming flu season, it is possible that we may see spikes in hospitalizations and ICU admissions that could overwhelm our health care system,” she said. “I strongly encourage people to get the flu vaccine and continue social distancing measures and masking to limit the spread of COVID-19.”
She adds, “Our findings underscore the importance of efforts for limiting transmission as well as ongoing investigations for effective therapies and vaccines.”
Natalie C. Cobb, MD, MPH
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About the Annals of the American Thoracic Society The AnnalsATS is a peer-reviewed journal published by the American Thoracic Society. The Journal delivers up-to-date and authoritative coverage of adult and pediatric pulmonary and respiratory sleep medicine and adult critical care. The scope of the Journal encompasses content that is applicable to clinical practice, the formative and continuing education of clinical specialists and the advancement of public health. The journal’s impact factor is 4.836.
Editor: Colin Cooke, MD, MS, associate professor in the department of internal medicine at the University of Michigan.
About the American Thoracic Society
Founded in 1905, the American Thoracic Society is the world's leading medical association dedicated to advancing pulmonary, critical care and sleep medicine. The Society’s more than 16,000 members prevent and fight respiratory disease around the globe through research, education, patient care and advocacy. The ATS publishes four journals, the American Journal of Respiratory and Critical Care Medicine, the American Journal of Respiratory Cell and Molecular Biology, Annals of the American Thoracic Society and ATS Scholar.