Some people may experience long-term symptoms — or 'long colds'— after acute respiratory infections that test negative for COVID-19, revealed researchers, who warned that these health impacts may currently be going unrecognised.
Long COVID is well-recognised, and acute respiratory infections due to other pathogens may also cause long-term symptoms. However, the authors of the new study alerted that few studies compared post-acute sequelae between SARS-CoV-2 and other acute respiratory infections.
For the study, published in The Lancet's eClinicalMedicine, researchers from Queen Mary University of London set out to compare the prevalence and severity of long-term symptoms after an episode of COVID-19 with those after an episode of another acute respiratory infection that tested negative for COVID-19. The study was the latest output from COVIDENCE UK – Queen Mary University of London's national study of COVID-19.
Health Impacts of Acute Respiratory Infection Going Unrecognised
Researchers analysed data from 10,171 UK adults — 1311 with SARS-CoV-2 infection (12.9%), 472 with non-COVID-19 acute respiratory infection, average age 62.8 years, 68.8% female, vast majority White — for 16 potential long COVID symptoms and health-related quality of life (HRQoL) reported between 21 January and 15 February, 2021.
The researchers found that "both types of infection were associated with increased prevalence/severity of most symptoms and decreased HRQoL compared with no infection". The more serious a bout of illness, the greater the chance of having long-term symptoms, they said.
Some of the most common symptoms of 'long cold' included coughing, stomach pain, and diarrhoea more than 4 weeks after the initial infection.
Participants with SARS-CoV-2 infection had increased odds of problems with taste/smell (odds ratio [OR] 19.74) and light-headedness or dizziness (OR 1.74) compared with participants who had non-COVID-19 acute respiratory infections. They also suffered more heart palpitations, sweating, and hair loss.
Those in the non-COVID group were more likely to have a cough or a hoarse voice than people with COVID. Both groups suffered breathlessness and fatigue.
Commenting to the Science Media Centre (SMC), Paul Harrison, professor of psychiatry at the University of Oxford, said that "COVID-19 infection was associated with a higher risk of several complaints, including memory problems, suggesting that 'brain fog' may be particularly related to the SARS-CoV-2 virus".
The findings suggested that there may be long-lasting health impacts following non-COVID acute respiratory infections such as colds, influenza, or pneumonia, that were "currently going unrecognised", warned the authors.
Recovery May Be Slow Regardless of Cause
Professor Adrian Martineau, COVIDENCE UK chief investigator and clinical professor of respiratory infection and immunity, Queen Mary University of London, expressed that the 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".
Giulia Vivaldi, researcher on COVIDENCE UK, Queen Mary University of London, and lead author, cautioned that a "lack of awareness, or the "lack of a common term", prevented both the reporting and the diagnosis of these conditions.
Peter Openshaw, professor of experimental medicine at Imperial College London, stressed that the term 'long cold' "should not belittle" the very significant disability that some with long COVID suffer.
In remarks to the SMC he said the study was important in showing that recovery from acute respiratory infection "may be slow regardless of cause", and that people should "expect a slow return to normality", and not expect to revert to full activities immediately after an acute respiratory infection from whatever cause.
More Understanding Needed
Dr David Strain, clinical senior lecturer and honorary consultant at the University of Exeter, said the researchers had demonstrated that "persistence of symptoms can be troubling, not just after COVID-19 but after many other infections". However, he pointed out that the concept of post-viral illness was already well established, with many in the UK living with myalgic encephalomyelitis (ME), many of whom reported a "rather benign" initial viral illness as the trigger.
While the severity of an illness appeared to be a key driver of risk of long-term symptoms, more research was being carried out to establish why some people suffer extended symptoms while others did not, according to the authors. They also cautioned that they did not have evidence to suggest the symptoms had the same severity or duration as long COVID.
The long-term symptoms experienced by some people with previous acute respiratory infections, including SARS-CoV-2, highlighted the "need for improved understanding, diagnosis, and treatment" of post-acute infection syndromes, said the authors.
Professor Adrian Martineau stressed that ongoing research would help get to the root of why some people experienced more prolonged symptoms than others, and could help identify the most appropriate form of treatment and care for those affected.