Much like with COVID-19, complications from the flu may linger after the patient recovers from the illness. According to research from Washington University School of Medicine, “long flu” may cause people who were hospitalized with the flu to experience some long-term, negative health issues. Long flu particularly impacts the lungs and airways. “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,” said Ziyad Al-Aly, MD, the study’s senior author. Flu actually presents a higher risk for long-term issues in the pulmonary system than COVID, the authors said, stressing that both long COVID and long flu are serious health concerns. 

The study used U.S. Department of Veterans Affairs data, including information about more than 81,000 people hospitalized for COVID between March 1, 2020, and June 30, 2022, and nearly 11,000 people hospitalized with seasonal flu between October 1, 2015, and February 28, 2019.

During the study period, people with COVID-19 experienced a 50% higher risk of death than flu. While COVID had a greater risk of impact on organ systems, flu was found to present greater risks to the pulmonary system. However, the authors concluded that infection with either illness created a significant risk of disability and disease.

“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,” said the senior author. While the study determined that, at least at the time, vaccination status didn’t impact results, Dr Al-Aly said, “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.”

Dr Al-Aly concluded, “Five years ago, it wouldn’t have occurred to me to examine the possibility of a ‘long flu.’” He added, “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.”