A new study from Queen Mary University of London, published in eClinicalMedicine, has found that people may experience long-term symptoms—or "long colds"—after acute respiratory infections that test negative for COVID-19.

Some of the most common symptoms of the "long cold" included coughing, stomach pain, and diarrhea more than four weeks after the initial infection. While the severity of an illness appears to be a key driver of risk of long-term symptoms, more research is being carried out to establish why some people suffer extended symptoms while others do not.

The findings suggest that there may be long-lasting health impacts following non-COVID acute respiratory infections, such as colds, influenza, or pneumonia, that are currently going unrecognized. However, the researchers do not yet have evidence suggesting that the symptoms have the same severity or duration as long COVID.

The research compared the prevalence and severity of long-term symptoms after an episode of COVID-19 vs. an episode of another acute respiratory infection that tested negative for COVID-19. Those recovering from COVID-19 were more likely to experience light-headedness or dizziness and problems with taste and smell compared to those who had a non-COVID-19 respiratory infection.

While long COVID is now a recognized condition, there have been few studies comparing long-term symptoms following SARS-CoV-2 coronavirus infection vs. other respiratory infections.

The study is the latest output from COVIDENCE UK, Queen Mary University of London's national study of COVID-19, launched back in 2020 and still in follow-up, with over 19,000 participants enrolled. This study analyzed data from 10,171 UK adults, with responses collected via questionnaires and statistical analysis carried out to identify symptom clusters.

Giulia Vivaldi, researcher on COVIDENCE UK from Queen Mary University of London and the lead author of the study, said, "Our findings shine a light not only on the impact of long COVID on people's lives, but also other respiratory infections. A lack of awareness—or even the lack of a common term—prevents both reporting and diagnosis of these conditions.

"As research into long COVID continues, we need to take the opportunity to investigate and consider the lasting effects of other acute respiratory infections.

"These 'long' infections are so difficult to diagnose and treat primarily because of a lack of diagnostic tests and there being so many possible symptoms. There have been more than 200 investigated for long COVID alone."

Professor Adrian Martineau, Chief Investigator of COVIDENCE UK and Clinical Professor of Respiratory Infection and Immunity at Queen Mary University of London, added, "Our findings may chime with the experience of people who have struggled with prolonged symptoms after having a respiratory infection despite testing negative for COVID-19 on a nose or throat swab.

"Ongoing research into the long-term effects of COVID-19 and other acute respiratory infections is important because it can help us to get to the root of why some people experience more prolonged symptoms than others. Ultimately this could help us to identify the most appropriate form of treatment and care for affected people."

Victoria King, said, "Barts Charity swiftly supported COVIDENCE UK in response to the outbreak of COVID-19 to help inform of its risk factors and impacts. These findings highlight not only the long-term symptoms experienced by people after COVID infection, but by people after other acute respiratory infections as well. As we learn more about long COVID symptoms and their possible treatments, studies like this help to build greater awareness around other prolonged respiratory infections that may be going unrecognized."