Patients infected with influenza and COVID-19 simultaneously are twice as likely to die

Research published in the Lancet has suggested that patients infected with influenza and COVID-19 simultaneously are twice as likely to die and over four times more likely to need ventilation support than just having COVID-19 alone.

As part of the International Severe Acute Respiratory and emerging Infection Consortium’s Coronavirus Clinical Characterisation Consortium, it’s the most extensive study to look at COVID-19 and other endemic respiratory viruses.

The researchers observed the clinical results of 212,466 patients co-infected with COVID-19 and either respiratory syncytial virus (RSV), influenza or an adenovirus who were admitted to a UK hospital between 6 February 2020 and 8 December 2021.

Tests for respiratory viral co-infections were performed on 6,965 COVID-19 patients, and viral co-infection was found in 583 of them. Of these, 220 had RSV, 227 had influenza viruses, and 136 had an adenovirus. The researchers calculated that the need for invasive mechanical ventilation increased by more than four times for patients who had co-infection with influenza and COVID-19 (odds ratio [OR] 4.14, 95 per cent confidence interval [CI] 2.00–8.49) after performing a weighted multivariable regression analysis. Those with COVID-19 and co-infection with adenovirus or RSV, on the other hand, did not require more mechanical ventilation.

In terms of in-hospital mortality, individuals who had both COVID-19 and influenza had a risk more than two times greater (OR 2.35, 95 per cent CI 1.07–5.12) than those who just had COVID-19 (OR 2.35, 95 per cent CI 1.07–5.12). It was also found that the risk of mortality increased in those who had co-infectious with adenoviruses (OR 1.53, 95% CI 0.67–3.33).

The authors stated: “First, our results provide further support for vaccination against both SARS-CoV-2 and influenza viruses. Second, they suggest that testing for influenza viruses is important in hospital in-patients with COVID-19 to identify patients at risk and a cohort of patients who might have different responses to immunomodulatory and antiviral therapy.”

Professor of experimental medicine at the University of Edinburgh, which was involved in the study, Kenneth Baillie, stated: “We found that the combination of COVID-19 and flu viruses is particularly dangerous. We expect that COVID-19 will circulate with flu, increasing the chance of co-infections. That is why we should change our testing strategy for COVID-19 patients in hospital and test for flu much more widely.”