Oxford study investigates prevalence and impact of long COVID

By James Gamble via SWNS

Persistent COVID-19 infections are "surprisingly common" with up to three in every 100 infections lasting for a month or longer, according to a new study.

Oxford University researchers found that some persistent infections had a high number of mutations of the virus - and that people with persistent infections were more than 50 percent more likely to report having Long COVID.

The new study, published in the journal Nature, suggests that those with persistent infections could act as 'reservoirs' that breed new deadly variants of the virus.

The belief that prolonged COVID-19 infections in immunocompromised people may have been the source of new variants, such as the Alpha and Omicron variants, has long been held amongst experts.

However, until now the prevalence of persistent infections across the general population and how the virus evolves in these situations has remained unknown.

The Oxford University team looked at data from the Office for National Statistics (ONS) COVID Infection Survey.

The survey tested participants on an approximately monthly basis.

Of the more than 90,000 participants, 3,603 provided two or more positive samples between November 2020 and August 2022 where the virus was sequenced.

A total of 381 of this number tested positive for the same viral infection over a period of a month or longer.

Within this group, 54 individuals had a persistent infection that lasted for at least two months.

The researchers therefore estimate that between one in a thousand and one in 200 (0.1-0.5%) of all infections may become persistent and last for at least 60 days.

In certain cases, individuals remained infected with variants that had already gone extinct in the general population.

In contrast, the researchers also found that reinfection with the same variant was very rare, which was likely due to the host developing immunity to that variant and the variant reducing in frequency to very low levels after a few months.

Out of the 381 persistent infections, 65 took three or more PCR tests during their infections.

The vast majority of these individuals (82%) demonstrated rebounding viral dynamics; experiencing high, then low, then high viral load dynamics - or how much of a virus remains in an infected person's blood.

The researchers say this demonstrates that the virus can lay low in an infected individual whilst maintaining the ability to actively replicate during prolonged infections.

They also found that those with persistent infections were 55 percent more likely to report having symptoms of Long COVID more than 12 weeks since the start of the infection in comparison with those with more typical infections.

Some individuals displayed an extremely high number of mutations, including mutations that define new coronavirus variants, alter target sites for monoclonal antibodies, and introduce changes to the coronavirus spike protein.

However, most individuals did not harbor a large number of mutations, suggesting that not every persistent infection will be a potential source for new concerning variants.

Study co-lead author Dr. Mahan Ghafari said: "Our observations highlight the continuing importance of community-based genomic surveillance both to monitor the emergence and spread of new variants, but also to gain a fundamental understanding of the natural history and evolution of novel pathogens and their clinical implications for patients."

Dr. Katrina Lythgoe, another co-lead author from the Pandemic Sciences Institute, added: "Although the link between viral persistence and Long COVID may not be causal, these results suggest persistent infections could be contributing to the pathophysiology of Long COVID.

"Indeed, many other possible mechanisms have been suggested to contribute to Long COVID including inflammation, organ damage, and micro thrombosis."