Covid-19 patients who have been hospitalised should also be routinely tested for flu, researchers have said. The call was made after the publication of a paper in the medical journal the Lancet that revealed having both conditions more than doubles the risk of a patient dying. Scientists also discovered that individuals who had contracted both Sars-CoV-2, the virus that causes Covid-19, and influenza viruses were more than four times more likely to require ventilation support and 2.4 times more likely to die than if they just had Covid-19. “We found that the combination of Covid-19 and flu viruses is particularly dangerous,” said Professor Kenneth Baillie of Edinburgh University. “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 study looked at more than 305,000 hospitalised patients with Covid-19 and involved researchers from Edinburgh University, Liverpool University, Imperial College London and Leiden University in the Netherlands. A total of 6,965 patients were found to have had Covid-19, while 227 also had the influenza virus. These individuals experienced significantly more severe outcomes, researchers found. “We were surprised that the risk of death more than doubled when people were infected by both flu and Covid-19 viruses,” said Professor Calum Semple of Liverpool University. “It is now very important that people get fully vaccinated and boosted against both viruses, and not leave it until it is too late.” This point was stressed by Professor Peter Openshaw of Imperial College London. “The vaccines that protect against Covid-19 and flu are different, and people need both. The way that these two infections are treated is also different so it’s important to test for other viruses even when you have a diagnosis in someone who is hospitalised with a respiratory infection.” The scientists’ warning comes as it was revealed that more than 600,000 people will be invited for a Covid-19 booster jab this week as infection levels climb close to record highs in England. About one in 16 people in private households in England – or 3.5 million people – are likely to have had Covid in the week to 19 March, according to the Office for National Statistics (ONS). This is up from one in 20 – or 2.7 million people – in the previous seven days and is the third week in a row that infections are estimated to have risen. Since rolling out the spring boosters last week, more than 470,000 people have come forward for a jab, NHS England said. It is asking people to wait to be invited before trying to book, with the Joint Committee on Vaccination and Immunisation recommending that eligible people get their vaccine six months after their initial booster for maximum effectiveness. About 5.5 million people in England aged over 75 or immunosuppressed will be able to get the booster. Researchers say the steep rise in infections across much of the country is being driven by the Omicron BA.2 variant, a more transmissible form of Omicron. The figures are further evidence that Covid-19 is becoming rapidly more prevalent in the UK and come as the number of people in hospital with the virus continues to increase. The percentage of people testing positive for Covid-19 in England has increased across all age groups and regions, the ONS found. Infection levels among the over-70s remain at their highest since estimates began in England in May 2020, with about one in 20 (5%) likely to have the virus, up week on week from one in 30 (3.5%). Covid-19 remains most prevalent among young children, however. About one in 12 (8.3%) of those aged between two and school year 6 are estimated to have had the coronavirus last week, up from one in 16 (6.3%)..