The prevalence of long covid, a term used to describe lingering symptoms after a covid-19 infection, has been a subject of debate throughout the pandemic. Tracy Beth Høeg and her colleagues at the University of California, San Francisco, claim that previous studies overestimated the likelihood of developing long covid. According to Høeg, more authoritative studies suggest that only a few percent of people are affected by long covid, rather than the half suggested by some studies with loose definitions or poor design.
Critics argue that Høeg's analysis ignores other well-designed studies that support the idea of lasting effects from the virus. One of the challenges in determining the true prevalence of long covid is the lack of understanding about its causes. Several explanations have been proposed, including the persistence of the virus in the body or immune system dysfunction, but it remains unclear which, if any, are correct. Additionally, long covid has similarities with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), another syndrome characterized by persistent tiredness after infections.
Some earlier studies of long covid relied on self-reported symptoms or surveys, which could be flawed since fatigue can be a symptom unrelated to infection. Høeg emphasizes the importance of comparing the rate of long covid symptoms in individuals after infection with a control group of people who did not contract the virus. However, some studies with control groups tended to include individuals in better health to begin with, which could skew the incidence of long covid.
One of the most authoritative studies conducted by the UK's Office for National Statistics found that 5 percent of people had long covid symptoms three to four months after infection, but so did 3.4 percent of people who were not infected. This suggests that 1.6 percent of people who contract the virus develop long covid.
While Høeg's analysis has garnered attention, it is unlikely to settle the debate. Critics argue that it oversimplifies a complex condition and insults those who experience long covid. They point to other studies that support higher prevalence rates. It is important to note that Høeg's analysis is not a systematic review and may have excluded other well-designed studies that support higher prevalence rates.
The exact number of people with long covid may not significantly impact affected individuals. Their main concern is finding ways to recover from the condition. Determining the best approaches to achieve that goal remains a challenge that requires further research.