Researchers have detected SARS-CoV-2 proteins in people with long Covid months after their initial infections, suggesting that persistent viral reservoirs may be associated with postacute sequelae of Covid-19. The findings do not conclusively identify persistent infections as a cause for this perplexing condition, nor do they immediately suggest new treatment options. But the research does provide important insight into this ongoing problem.
The results of the study were published on Tuesday in Clinical Microbiology and Infection.
Since the beginning of the pandemic, many people have experienced myriad symptoms that can continue for months after their initial infection. The extent of the problem is hard to gauge. In one report, researchers estimated that 5.8 million children in the U.S. may have long Covid. According to data provided by the CDC, nearly 18% of all adults in the U.S. say that have experienced long Covid.
Part of the difficulty in assessing the extent of the problem is that long Covid, or PASC, can present in many ways. People often report fatigue and brain fog. But respiratory, digestive, and neurologic symptoms also have been reported. To account for these varied symptoms, an expert committee convened by the National Academies of Sciences, Engineering, and Medicine recently recommended that PASC should be defined as, “an infection-associated chronic condition that occurs after SARS-CoV-2 infection and is present for at least three months as a continuous, relapsing and remitting, or progressive disease state that affects one or more organ systems.”
There is no conclusive test for long Covid. There are no reliable treatment modalities for long Covid.
To better understand the etiology of long Covid, researchers at several institutions in the U.S. studied over 700 people who had prior laboratory-confirmed SARS-CoV-2 infections. They specifically looked for the presence of viral proteins in their blood at least one month after infection and determined if they reported one or more symptoms commonly associated with PASC.
The results? People reporting symptoms associated with PASC were about twice as likely to have SARS-CoV-2 proteins in their blood as people who did not report PASC-related symptoms.
One possible interpretation of these results is that a persistent viral reservoir may contribute to the development of long Covid. Typically, viruses are eliminated from the body shortly after an acute infection. But in some cases, virus particles remain, often hidden and undetectable. The detection of viral proteins up to 14 months after acute infections certainly is consistent with this scenario. And the correlation between the presence of viral proteins and reported PASC symptoms is intriguing.
But the correlation clearly isn’t perfect. Not everyone in the study with detectable viral proteins in their blood reported PASC symptoms. And not everyone with long Covid had detectable viral proteins.
Long Covid remains a vexing problem. It is a very real, and potentially very debilitating outcome of SARS-CoV-2 infections. But like ME/CFS, it is difficult to diagnose and treat. If persistent SARS-CoV-2 infections contribute to the development of long Covid, then aggressive antiviral treatments may be a viable treatment modality. At this point, though, the association remains unclear.
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