We focused on long-term symptoms by only including people who had been infected more than four weeks earlier. We also took into account people’s general health before they were infected, and whether they had any existing respiratory conditions.
Our study showed that all the symptoms considered were more common in people with previous COVID than in people with no infections, regardless of whether they reported long COVID. But this finding wasn’t unique to COVID. Almost all the symptoms we looked at were also more common in people with non-COVID respiratory infections than in those with no infection.
In other words, our findings hinted towards the existence of a “long cold”: long-lasting health effects from other respiratory infections, such as colds, flu, or pneumonia, that are currently going unrecognised.
Some of the most common symptoms of the long cold include coughing, stomach pain, and diarrhoea. These symptoms were reported an average of 11 weeks after the infection. While a severe initial infection seems to increase the risk of long-term symptoms, our research does not yet tell us why some people suffer extended symptoms while others do not.
Importantly, we have no evidence that symptoms of the long cold have the same severity or duration as long COVID. In fact, we saw some important differences in the symptoms reported in the two groups, with those recovering from COVID more likely to experience light-headedness or dizziness and problems with taste and smell.
These findings shine a light not only on the impact of long COVID on people’s lives, but also other respiratory infections.