26/08/2025
Scientists find viral proteins in the blood of patients with long COVID.
A new study has found fragments of the COVID-19 virus lingering in the blood of people suffering from long COVID – months after their initial infection. These tiny protein remnants, often called “ghost proteins,” may represent the first measurable biomarker for a condition that has remained difficult to diagnose.
The research, published in the journal Infection, was led by scientists at the Translational Genomics Research Institute (TGen) and the Lundquist Institute at Harbor-UCLA Medical Center. By analyzing blood samples from long COVID patients, the team found 65 unique viral protein fragments hidden inside microscopic particles known as extracellular vesicles (EVs). These are small packages cells use to move materials like proteins and metabolites around the body.
Crucially, the viral proteins came from a molecule called Pp1ab, which the virus uses to replicate itself. Because this protein doesn’t exist in healthy human cells, its presence could indicate that parts of the virus remain in the body – even after recovery from the initial infection.
Why is this important?
Many scientists suspect long COVID symptoms – including fatigue, brain fog, and shortness of breath – may be caused by hidden viral reservoirs that persist in the body. These findings support that theory, suggesting that the body could still be processing viral debris weeks or even months after the infection ends.
Interestingly, the viral fragments weren’t found in every blood draw, which raises questions about whether this activity is ongoing or sporadic – and whether triggers like physical exertion may influence it.
If confirmed, this discovery could lead to the first reliable blood test for long COVID, offering hope for more accurate diagnoses and targeted treatments.
Read the study:
Abbasi, Asghar et al. "Possible long COVID biomarker: identification of SARC-CoV-2 related protein(s) in Serum Extracellular Vesicles." Infection, 21 July 2025.