New research provides clues about the cause of long Covid

Researchers have discovered SARS-CoV-2 proteins in people with long Covid months after their initial infections, suggesting that persistent viral reservoirs may be associated with post-acute consequences of Covid-19. The findings do not convincingly identify persistent infections as the cause of this baffling condition, nor do they immediately suggest new treatment options. But the research does provide important insight into this persistent problem.

The results of the study were published on Tuesday in Clinical microbiology and infection.

Since the pandemic began, many people have experienced numerous symptoms that can last months after their initial infection. The scale of the problem is difficult to estimate. In one report, researchers estimate that 5.8 million children in the US may have a long bout of Covid. According to data provided by the CDCNearly 18% of all US adults say they have experienced long-term Covid.

Part of the difficulty in assessing the scale of the problem is that long Covid, or PASC, can present itself in many ways. People often report fatigue and brain fog. But respiratory, digestive and neurological symptoms have also been reported. To account for these diverse symptoms, an expert committee convened by the National Academies of Sciences, Engineering, and Medicine recently recommended that PASC be defined as “an infection-associated chronic condition that occurs following a SARS-CoV 2 infection and is present for at least three months as a continuous, relapsing and remitting or progressive disease state affecting 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-19, researchers from several institutions in the US studied more than 700 people who had previously had 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 whether they reported one or more symptoms often associated with PASC.

The results? People who reported symptoms related to PASC were about twice as likely to have SARS-CoV-2 proteins in their blood as people who did not report PASC-related symptoms.

A possible interpretation of these results is that a persistent viral reservoir may contribute to the development of long Covid-19. Typically, viruses are eliminated from the body shortly after an acute infection. But in some cases, virus particles remain behind, often hidden and undetectable. The detection of viral proteins up to 14 months after acute infections certainly fits into this scenario. And the correlation between the presence of viral proteins and reported PASC symptoms is intriguing.

But the correlation is clearly not perfect. Not everyone in the study with detectable viral proteins in the blood reported PASC symptoms. And not everyone with long Covid-19 had detectable viral proteins.

Long Covid remains a difficult problem. It is a very real and potentially very disabling outcome of SARS-CoV-2 infections. But like ME/CFSit is difficult to diagnose and treat. If persistent SARS-CoV-2 infections contribute to the development of long-term Covid-19, aggressive antiviral treatments may be a viable treatment modality. However, at this time the association remains unclear.