Covid-19 mixed with flu raises risk of severe illness
Adults in hospital who have Covid-19 and flu at are at much greater risk of severe disease and death than those who have Covid-19 alone or with other viruses, research shows.
Patients with co-infection of SARS-CoV-2, which causes Covid-19, and influenza viruses were over four times more likely to require ventilation support and 2.4 times more likely to die than if they only had Covid-19, experts found.
Researchers say the findings show the need for greater flu testing of Covid-19 patients in hospital and highlight the importance of full vaccination against both Covid-19 and the flu.
The team from the University of Edinburgh (Roslin Institute, Centre for Inflammation Research and Usher Institute), University of Liverpool, Leiden University and Imperial College London, made the findings in a study of more than 305,000 hospitalised patients with Covid-19.
The research – delivered as part of the International Severe Acute Respiratory and emerging Infection Consortium’s (ISARIC) Coronavirus Clinical Characterisation Consortium – is the largest study to date of people with Covid-19 and other endemic respiratory viruses.
ISARIC’s study was set up in 2013 in readiness for a pandemic such as this. The team looked at the data of adults who had been hospitalised with Covid-19 in the UK between 6 February 2020 and 8 December 2021.
Test results for respiratory viral co-infections were recorded for almost 7,000 patients with Covid-19. Some 227 of these also had flu, and they experienced significantly more severe outcomes.
Dr Maaike Swets, PhD student at the University of Edinburgh and Infectious Diseases department, Leiden University Medical Centre, said; ” In the last two years we have frequently witnessed patients with Covid-19 become severely ill, at times leading to an ICU admission and the employment of an artificial ventilator to help with breathing. That an influenza infection could give rise to a similar situation was already known, but less was understood about the outcomes of a double infection of SARS-CoV-2 and other respiratory viruses.”
Professor Kenneth Baillie, Professor of Experimental Medicine, University of Edinburgh, added; “ We found that the combination of Covid-19 and flu viruses is particularly dangerous. This will be important as many countries decrease the use of social distancing and containment measures. 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.”
The findings have been published a research letter in The Lancet.
The research was funded by UK Research and Innovation (UKRI) and by the Department of Health and Social Care through the National Institute for Health Research (NIHR) as part of the UK Government’s Covid-19 rapid research response.