Researchers at the Institute of Liver and Biliary Sciences have identified a potential hidden reservoir of the COVID-19 virus that might explain its persistence and recurrence.

Their study aimed to investigate the presence of the virus inside the extracellular vesicles (EVs) -- microscopic particles released by cells -- in patients with and without chronic liver disease (CLD).

The findings, published in the journal Liver Research, showed that SARS-CoV-2 RNA was present in EVs in individuals who tested negative via standard RT-PCR methods.

Even for individuals deemed virus-free by conventional tests, the presence of SARS-CoV-2 RNA within EVs may indicate a potential source for recurrent infections.

Moreover, these infected EVs have demonstrated the ability to transmit the virus to previously unaffected cells in laboratory settings, pointing to a previously unrecognised route of transmission.

“The identification of SARS-CoV-2 RNAs in the EVs in patients with negative RT-PCR indicates the persistence of infection and likely recurrence of the infection. It is suggestive of another route of transmission as EVs harbour SARS-CoV-2 RNAs,” said lead author Sukriti Baweja, from the Institute’s Department of Molecular and Cellular Medicine.

"EV-associated RNAs may determine the ongoing inflammation and clinical course of subjects with undetectable SARS-CoV-2 virus and this may have relevance to better management of patients with CLD."

"The identification of SARS-CoV-2 RNA in EVs underscores the need to explore alternative diagnostic methods that leverage this discovery, potentially revolutionising our ability to detect and manage COVID-19  infections more effectively," Baweja explained.

Current diagnostic tools, while valuable, have limitations, including occasional false negatives due to factors such as sample collection technique and viral load.

Detecting SARS-CoV-2 RNA within EVs might offer a more sensitive and rapid diagnostic approach, potentially aiding in identifying individuals with persistent or recurrent infections.

Furthermore, the presence of SARS-CoV-2 RNA in EVs, not only in respiratory samples but also in plasma, enables more opportunities to understand the virus's behaviour beyond the respiratory tract.

These insights into the underlying mechanisms of viral persistence and recurrence offer new avenues for therapeutic interventions.