Don’t belittle most viral infections by regarding them as somewhat inconsequential, for they can be major drivers of chronic diseases. This is what a team of researchers found as they noted  that people hospitalised with seasonal influenza also can suffer long-term, negative health effects, especially involving their lungs and airways as in the case with the Covid-19.

The study comparing the viruses that cause Covid-19 and the flu also revealed that in the 18 months after infection, patients hospitalized for either Covid-19 or seasonal influenza faced an increased risk of death, hospital readmission, and health problems in many organ systems. Further, the time of highest risk was 30 days or later after initial infection, said the findings published in The Lancet Infectious Diseases.

However, the overall risk and occurrence of death, hospital admissions, and loss of health in many organ systems are substantially higher among Covid-19 patients than among those who have had seasonal influenza.

The study is conducted by researchers from Washington University School of Medicine in St. Louis and the Veterans Affairs St. Louis Health Care System.

“The study illustrates the high toll of death and loss of health following hospitalization with either Covid-19 or seasonal influenza,” said senior author Ziyad Al-Aly, a clinical epidemiologist at Washington University.

“It’s critical to note that the health risks were higher after the first 30 days of infection. Many people think they’re over Covid-19 or the flu after being discharged from the hospital. That may be true for some people. But our research shows that both viruses can cause long-haul illness.”

The statistical analysis spanned up to 18 months post-infection and included a comparative evaluation of risks of death, hospital admissions and 94 adverse health outcomes involving the body’s major organ systems.

“A review of past studies on Covid-19 versus the flu focused on a short-term and narrow set of health outcomes,” said Al-Aly, who treats patients within the VA St. Louis Health Care System and is an assistant professor of medicine at Washington University.

“Our novel approach compared the long-term health effects of a vast array of conditions. Five years ago, it wouldn’t have occurred to me to examine the possibility of a ‘long flu.’

“A major lesson we learned from SARS-CoV-2 is that an infection that initially was thought to only cause brief illness also can lead to chronic disease. This revelation motivated us to look at long-term outcomes of Covid-19 versus flu,” he said.

“We wanted to know whether and to what degree people with flu also experience long-term health effects,” Al-Aly said. “The big answer is that both Covid-19 and the flu led to long-term health problems, and the big aha moment was the realization that the magnitude of long-term health loss eclipsed the problems that these patients endured in the early phase of the infection. Long Covid is much more of a health problem than Covid, and long flu is much more of a health problem than the flu.”

However, the overall risk and occurrence of death, hospital admissions, and loss of health in many organ systems are substantially higher among Covid patients than among those who have had seasonal influenza, Al-Aly said.

Regarding both viruses, patient vaccination status did not affect results.

Those in the Covid-19 cohort were hospitalized during the pre-delta, delta and omicron eras.

During the overall 18-month study period, patients who had Covid-19 faced a 50% higher risk of death than those with seasonal influenza. This corresponded to about eight more deaths per 100 persons in the COVID-19 group than among those with the flu.