is that becuase this condition is relativly new or peopele are just not followed

The short version: the evidence here does not answer whether prolonged cases are due to newness or poor follow-up, because it contains no long-term cohort study that tracks people from infection through year two or three.

The retrieval surfaced a 2023 prospective cohort that followed 235 people for 24 months, but only 121 completed the study. At 24 months, 62% still had symptoms [10]. That is a high number, but the study lost half its participants, which is exactly the kind of follow-up problem you are asking about. People who drop out may be the ones who recovered, or the ones who got too sick to stay in the study. You cannot tell.

The 2025 review of global epidemiology found that prevalence actually looked higher at 1-2 years (47%) than at under 1 year (35%) [12]. That is the opposite of what you would expect if people were steadily recovering. But that comparison comes from pooling different studies with different methods, not from following the same people over time. It could reflect who gets studied, not who gets better.

What is missing is a study that enrolls a large group at infection, measures symptoms the same way every few months, and keeps most people in the study for two or three years. Without that, you cannot separate the natural history of the condition from the artifacts of how it is measured. The condition is new enough that such studies are still running. The 24-month cohort [10] is the longest here, and it lost half its people.

My call: the evidence is not clear on whether prolonged cases reflect the condition's true course or poor follow-up, because the longest study here lost half its participants. Confidence: low.