‘Long flu’ is a real illness just like long COVID, study explains

ST. LOUIS — A new study suggests that people can experience ‘long flu,’ a condition similar to long COVID. Since the outbreak of COVID-19, scientists have explored how the virus can affect various organ systems, often resulting in long-term, disabling health issues, a phenomenon known as ‘long COVID.’

There have been frequent comparisons between COVID-19 and influenza, particularly regarding common symptoms like fever, headaches, and coughing. Recent research, however, has identified another similarity: the long-term impacts of these illnesses.

Conducted by a team from the Washington University School of Medicine and the Veterans Affairs St. Louis Healthcare System, this study discovered that people hospitalized with the flu may endure prolonged, adverse health effects, particularly concerning their lungs and airways.

Moreover, the study found that in the 18 months following hospitalization for the flu, patients were at an increased risk of death, organ health issues, and hospital readmission, mirroring the patterns observed in patients hospitalized for COVID-19.

“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,” says senior author Ziyad Al-Aly, MD, a clinical epidemiologist at Washington University, in a media release.

“We wanted to know whether and to what degree people with flu also experience long-term health effects, and the answer is that the flu can lead to long-term health problems – just like COVID-19.”

The researchers also noted that the risk to health was highest after the first month of infection – refuting the commonly-held notion that these kinds of diseases are short-term ones.

“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,” Dr. Al-Aly continues.

Doctor listening to coronavirus / COVID-19 patient having trouble breathing
(© Алина Троева – stock.adobe.com)

The study indicates that both viruses can lead to prolonged suffering, but the risk of death and health deterioration is significantly higher in COVID-19 patients compared to those with the flu. A key difference lies in the nature of the viruses: while the flu predominantly affects the respiratory system, COVID-19 has a more indiscriminate impact, potentially damaging any organ system.

“This shows that the flu is primarily a respiratory virus, as has been believed for the past century. In contrast, COVID-19 is more aggressive and non-selective, attacking not just the lungs but also other organs, leading to more severe or fatal conditions involving the heart, brain, kidneys, and others,” explained Dr. Al-Aly.

To conduct this study, researchers analyzed anonymized medical records from a database maintained by the U.S. Department of Veterans Affairs, the nation’s largest integrated healthcare system. The study examined 81,280 patients hospitalized for COVID-19 between March 1, 2020, and June 30, 2022, and 10,985 patients hospitalized for influenza from Oct. 1, 2015, to Feb. 28, 2019. It assessed the health effects over the subsequent 18 months.

Findings revealed that infection and hospitalization due to either virus increased the risk of disability and disease, though the severity varied. Patients hospitalized with COVID-19 faced a 68-percent increased risk of health issues across all organ systems, whereas flu patients had a six-percent increased risk, mostly involving the respiratory system.

The primary distinction between the diseases was the death risk. COVID-19 patients were 50 percent more likely to die than flu patients. Additionally, COVID-19 patients had a higher likelihood of hospital readmission and ICU admission. For every 100 individuals, there were 20 more hospital admissions and nine more ICU admissions for COVID-19 compared to the flu.

“Our findings highlight the continued need to reduce the risk of hospitalization for these two viruses as a way to alleviate the overall burden of health loss in populations,” the study author says. “For both COVID-19 and seasonal influenza, vaccinations can help prevent severe disease and reduce the risk of hospitalizations and death. Optimizing vaccination uptake must remain a priority for governments and health systems everywhere. This is especially important for vulnerable populations such as the elderly and people who are immunocompromised.”

“Before the pandemic, we tended to belittle most viral infections by regarding them as somewhat inconsequential: ‘You’ll get sick and get over it in a few days.’ But we’re discovering that is not everyone’s experience. Some people are ending up with serious long-term health issues. We need to wake up to this reality and stop trivializing viral infections and understand that they are major drivers of chronic diseases,” Al-Aly concludes.

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South West News Service writer Imogen Howse contributed to this report.

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