According to a recent study based on viral sequence data from a national infection survey, researchers have identified 381 individuals with SARS-CoV-2 RNA at high titre persisting for at least 30 days, with 54 cases showing viral RNA persisting for at least 60 days. These cases are referred to as 'persistent infections', hinting at ongoing viral replication. Individuals with persistent infections had over 50% higher odds of reporting long COVID symptoms compared to those with non-persistent infections.

The study estimates that 0.1-0.5% of infections may become persistent, with viral loads rebounding and lasting for at least 60 days. The research also revealed significant evolutionary dynamics within these persistent infections, with some individuals showing numerous viral amino acid substitutions, indicating strong positive selection, while others had no consensus change in sequences for extended periods, reflecting weak selection. These substitutions included mutations characteristic of SARS-CoV-2 variants, target sites for monoclonal antibodies, and commonly found in immunocompromised individuals.

The findings have far-reaching implications for understanding SARS-CoV-2 infection, epidemiology, and evolution, shedding light on the potential role of persistent infections as viral reservoirs that could contribute to future outbreaks and the emergence of highly divergent virus lineages.