Persistent Covid-19 lasting in a patient for more than two years has led to the novel coronavirus developing dozens of new mutations in the individual, researchers discovered in a new study.
The study, published in The Lancet Microbe, describes one of the longest known Sars-CoV-2 infections lasting over 750 days in a person with advanced HIV infection.
While there was no onward transmission of new variants of the virus from the person, the findings emphasise the need for surveillance and treatment in people with persistent Covid-19 infections, researchers said.
Scientists analysed eight samples collected between March 2021 and July 2022 from the patient presumed to have been infected first in May 2020.
They found that the virus specimen from the patient carried dozens of mutations and within the B.1 lineage of the novel coronavirus to which the highly infectious omicron variant also belongs.
Scientists found mutations associated with the omicron variant of the novel coronavirus appeared in this long-term infection patient “months before their emergence in the community following the omicron surge at the end of 2021”.
“We observed the rise and fall of different combinations of mutations at different times of infection, supporting the idea that in long-term SARS-CoV-2 infections, the dominant genome can change over time and multiple viral populations can persist in a single infection,” scientists wrote.
Researchers then used software tools to analyse the viral genome and its evolution within the patient.
Most of the virus mutations found in the patient were not found in online databases, hinting there were no concerning transmissions descending from this individual.
“The inferred absence of onward infections might indicate a loss of transmissibility during adaptation to a single host,” researchers wrote in the study.
The findings confirm that persistent Covid-19 in people with compromised immunity are a plausible source of the emergency of variants of concern.
“Our results underscore the importance of appropriate treatment to cure persistent SARS-CoV-2 infections and monitoring them to understand how mutations contribute to viral adaptation,” researchers wrote.
“The body of evidence surrounding the evolution of these persistent infections provides justification for further efforts to reduce infection risk among vulnerable, immunocompromised populations and the further study of intrahost SARS-CoV-2 evolution,” they added.
The study also points to the parallel evolution of the coronavirus, following a similar trajectory into the emergence of the same omicron variant in different patients.
“Convergent SARS-CoV-2 evolution, both in and outside the spike protein, observed in this study suggests parallels with the evolutionary process leading to emergence of the omicron VOC,” researchers wrote.
