Scientists Discovery How COVID Variants Change in Chronic Infections
Scientists reassured the people in the first months of the COVID-19 epidemic that the SARS-CoV-2 virus mutates somewhat slowly. This resulted in the belief that vaccines may provide long-lasting protection since the virus would not mutate significantly very quickly. But over time, this presumption was called into doubt. Beginning to mutate faster, the virus became more transmissible, more skilled at avoiding immunity, and finally caused breakthrough infections and reinfections.
The SARS-CoV-2 Hidden Evolutionary Pathway
Although experts were right to say that the virus mutates modestly as it passes from person to person, they could not foresee another evolutionary path. Once SARS-CoV-2 enters an immunocompromised person, it can linger in the body for months and accumulate many mutations during this protracted infection. Highly modified variants of the virus can arise from this extended evolution inside one host and, in rare circumstances, can be passed on to others.
The Omicron variant’s arrival in late 2021 is one of the most notable instances of these phenomena. Omicron carried around fifty mutations, an evolutionary jump matched to many years of viral evolution compressed into few months. This let it create large waves of infection even in those who had vaccinations. Scientists currently think that the formation of novel variations including Omicron and its descendants is mostly caused by persistent infections in immunocompromised patients.
Early Signals of Chronic Infections
Researchers in New York had started looking at cancer patients with extended COVID-infections as early as March and April 2020. These individuals tested positive for SARS-CoV-2 for up to two months, their immune systems compromised by their diseases and treatments. According to a December 2020 study, such individuals could require extended isolation times to stop possibly mutant virus strains from spreading.
An other study conducted outside of the United Kingdom confirmed this theory even more. Under the direction of Ravindra Gupta, researchers found an immunocompromised patient whose residual infection guided the virus to acquire mutations improving its capacity to infect human cells and avoid immune reactions. Although the patient received antibodies from recovered COVID-19 patients, the virus changed to fit these antibodies instead of being eradicated. This implied that immunocompromised people can be incubators for novel viral adaptations, therefore giving the virus chances to improve its capacity to spread and withstand immune responses.
Monitoring Variants’ Development
Although no specific COVID variant has been proven to be connected to a particular immunocompromised patient, mounting data point to several of them having evolved in this manner. Although the rest of the DNA stays mostly unaltered, scientists have found a clear mutation pattern linked with chronic infections—many changes in the spike protein the virus employs to enter human cells. Omicron subvariants include BA.1 and BA.2 as well as JN.1, which sparked an epidemic last winter, clearly show this trend.
Researcher specializing in viral evolution at the Fred Hutchinson Cancer Center Jesse Bloom has said he now has “very high confidence” these variants started from chronic infections. While the roots of other varieties are still unknown, many would have followed a similar evolutionary route.
Looking Ahead: Is Future Variants Predicted by Chronic Infections?
Scientists noted a similar inclination in influenza viruses even before COVID. Bloom and colleagues investigated flu evolution in immunocompromised patients in 2017 and discovered several mutations in these individuals later showed up in seasonal flu strains. This inspired the theory that tracking persistent infections would provide understanding of how viruses change with time.
Researchers are now using the same method on SARS-CoV-2. Under Harm van Bakel and Viviana Simon, scientists at the Icahn School of Medicine at Mount Sinai are creating better sequencing methods to precisely examine persistent illnesses. Their aim is to find which immunocompromised people most likely have long-term infections and whether these cases could suggest the next major mutation.
Although COVID-19 monitoring has lost urgency, knowledge of how persistent infections impact the evolution of the virus is still absolutely vital. Tracking these recurring diseases helps scientists to predict new varieties and enhance plans of action to stop further outbreaks.
