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HomeNEWS&BLOGSThe Lancet: Co-infection with COVID-19 and Influenza Increases the Risk of Severe Illness and Death

The Lancet: Co-infection with COVID-19 and Influenza Increases the Risk of Severe Illness and Death


On March 25, 2022, researchers from the University of Edinburgh, University of Liverpool, Leiden University and Imperial College London published a paper on The Lancet: SARS-CoV-2 co-infection with influenza viruses, respiratory syncytial viruses, or adenoviruses.

The research team’s study of more than 300,000 hospitalized patients with COVID-19 found that adults infected with both the COVID-19 and the flu have a significantly increased risk of severe illness and death compared with those infected with the COVID-19 alone. Specifically, the risk of needing ventilator treatment was 4.14 times, and the risk of death was 2.35 times.


The study is part of the research of COVID-19 clinical symptoms by ISARIC, and is the largest study of people infected with COVID-19 and other endemic respiratory viruses till now. The ISARIC was formed in 2013 to prepare for a respiratory virus pandemic.

The research team searched data from more than 305,000 adults hospitalized with COVID-19 in the UK between 6 February 2020 and 8 December 2021.Among them, 6,965 people were also detected to be infected with the respiratory virus during the COVID-19 hospitalization. Of those, 227 were co-infected with the flu virus, and those people experienced more severe symptoms. Specifically, patients who infected with the flu virus while hospitalized for COVID-19 infection had a 4.14 times higher risk of developing a ventilator and a 2.35 times higher risk of death than those hospitalized with COVID-19 alone.


Dr. Maaike Swets, the first author of the paper, said that in the more than two years of the COVID-19 pandemic, we have often witnessed COVID-19 infected people become seriously ill, and sometimes even need to enter ICU and use a ventilator for treatment. The flu virus can also cause these similarly severe symptoms. But little is known about the consequences of co-infection with COVID-19 and other respiratory viruses.

And this statistic clearly tells us that it is particularly dangerous to be infected with the COVID-19 and influenza virus at the same time. At present, many countries have begun to liberalize the social distancing policy of the COVID-19, which will lead to the simultaneous transmission of the COVID-19 and flu, increasing the chance of co-infection. Therefore, the current testing strategy for hospitalized patients with COVID-19 should be changed and influenza testing should be more widely available.

The authors of the paper said that simultaneous infection with the COVID-19 and influenza viruses is not common, but it is important to realize that this situation is actually happening, and when it occurs, it will greatly increase the risk of severe illness and death. The treatment of COVID-19 infection and influenza virus infection is not the same, so it is necessary to conduct flu testing at the same time in hospitalized patients with COVID-19 virus.

At the same time, this study also emphasizes the importance of vaccination against the COVID-19 and influenza.




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