Covid mixed with flu increases severe illness, death risk: Lancet

Adults who have been hospitalised due to Covid-19 and flu at the same time are at much greater risk of severe disease and death compared to patients who have just contracted Covid or any other viruses, new research shows.

The study, published in The Lancet journal, indicated that 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.

"We found that the combination of Covid and flu viruses is particularly dangerous. This will be important as many countries decrease the use of social distancing and containment measures," said researcher Kenneth Baillie from the University of Edinburgh.

"We expect that Covid will circulate with flu, increasing the chance of co-infections. That is why we should change our testing strategy for Covid patients in hospital and test for flu much more widely," Baillie added.

The researchers say the findings show the need for greater flu testing of Covid patients in hospital and highlight the importance of full vaccination against both Covid and the flu.

For the study, the team involved more than 305,000 hospitalised patients with Covid in the UK between February 6, 2020 and December 8, 2021.

Test results for respiratory viral co-infections were recorded for 6,965 patients with Covid. At least 227 of these also had the influenza virus, and they experienced significantly more severe outcomes.