Lingering respiratory virus symptoms aren't limited to COVID, new review shows

PonyWang / iStock For many people who contract COVID-19, the initial infection comes with a set of worrisome symptoms, from muscle aches and fatigue to trouble breathing—and for a subset of those people, symptoms persist beyond the acute infection phase. Long COVID has become a well-known post-viral condition that can take a significant toll on health and quality of life. But SARS-CoV-2 isn't the only virus that can have lingering aftereffects. Other respiratory viral infections (RVIs), which affect millions of people every year, can trigger persistent physical, cognitive, and psychiatric symptoms. A new systemic review published in Respirology examined the size and scope of persistent symptoms following non-COVID respiratory infections like influenza and respiratory syncytial virus (RSV). 'Understanding post-acute sequelae of non–COVID-19 RVIs, given their global burden and relative undercharacterisation, is important to guide clinical care and public health policy,' write the researchers, who were led by a team from Duke-NUS Medical School in Singapore. For the review, researchers analyzed 13 observational studies involving 631,863 people from January 2004 to August 2025. The flu was the most studied infection, and lung dysfunction was the most frequently reported persistent symptom. In a small 2009 study (48 participants), 54% of participants had abnormal pulmonary function 11 to 13 months after acute influenza infection. Roughly one-third reported persistent respiratory symptoms one year after infection, and over 40% reported reduced exercise tolerance. In another small study (47 participants), this one from 2017, 78% of people who survived severe flu infection had reduced ability to transfer oxygen from their lungs into their bloodstream two years later. Understanding post-acute sequelae of non–COVID-19 RVIs, given their global burden and relative undercharacterisation, is important to guide clinical care and public health policy. Findings from larger studies mirrored those from the smaller studies. Among 951 Australians diagnosed as having influenza, 23% reported symptoms after 12 weeks, and 4.4% had moderate-to-severe difficulty carrying out everyday activities. A US study of 20,844 hospitalized patients found that one in 10 still had a cough or shortness of breath six months after infection. An analysis of German insurance data from nearly 570,000 people found that 23% reported memory problems, and 44% had a distorted sense of taste or a reduced sense of smell three to six months after acute illness. Two of the 13 studies in the review looked at RSV and found that cardiovascular complications were the most common persistent post-viral complaint. Among 441 US adults hospitalized with RSV, 16% experienced a heart-related event from 29 days to six months after acute infection, making the monthly rate of cardiovascular events 1.6 times higher during the post-infection period than during the six months before hospitalization. A cohort study of 1,553 adults with RSV in Singapore found that 2.1% experienced new-onset cardiac disorders after infection. The review included one small study of human metapneumovirus. Among 92 hospitalized adults, 55% reported at least one persistent symptom three to nine months after infection. Shortness of breath was most common (29%), followed by fatigue (17%), and cough (17%). The authors caution that most studies included in the review were observational and focused on hospitalized patients, making it difficult to know how often lingering symptoms occur after milder infections. They also note differences in outcome measures and follow-up approaches between the studies, concluding that future studies should use standardized definitions and outcome measures 'to better define disease burden and inform targeted follow-up and prevention strategies.'