Patients with both Covid and flu four times more likely to fall seriously ill

Covid hosital patients who also flu have a significantly higher risk of severe illness and death, a study has shown.

Those with both Covid and influenza were more than four times more likely to require a ventilator and at twice the risk of dying.

The findings highlight the importance of testing Covid patients in hospital for the flu too, as well as full vaccination against both conditions.

Some 350,000 patients who had been hospitalised with the virus between 6 February 2020 and 8 December 2021 were analysed by researchers from University of Edinburgh, University of Liverpool, Leiden University and Imperial College London.

They found test results for respiratory viral co-infections were recorded for 6965 patients, with some 227 of the patients also having the influenza virus.

These patients went on to experience significantly more severe outcomes leading to the conclusions the combination of Covid and the flu was “particularly dangerous”.

The research – delivered as part of the International Severe Acute Respiratory and emerging Infection Consortium’s (ISARIC) Coronavirus Clinical Characterisation Consortium – is the largest ever study of people with Covid-19 and other endemic respiratory viruses.

“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. We expect that Covid will circulate with flu, increasing the chance of co-infections,”said Professor Kenneth Baillie, Professor of Experimental Medicine at the University of Edinburgh..

“That is why we should change our testing strategy for Covid-19 patients in hospital and test for flu much more widely.”

The researchers stressed the importance of having both the Covid and flu jabs - which is offered to those over 50, the immunosuppressed, pregnant women, and those who live in residential care or look after them, and frontline health care workers.

Professor Calum Semple, professor of Outbreak Medicine and Child Health at the University of Liverpool, said: “We are seeing a rise in the usual seasonal respiratory viruses as people return to normal mixing. So, we can expect the flu to be circulating alongside Covid-19 this winter. We were surprised that the risk of death more than doubled when people were infected by both flu and Covid-19 viruses.

“It is now very important that people get fully vaccinated and boosted against both viruses, and not leave it until it is too late.”