When it comes to COVID-19, it’s easy to only focus on the virus that causes it, SARS-CoV-2. But other factors may be at play when it comes to how COVID-19 affects people.
A study published in Nature was able to evaluate the reactivation of dormant viruses in people with COVID-19.
Researchers found that the reactivation of certain viruses occurred, and their activation was linked to both acute COVID-19 severity and possibly to long COVID as well.
Overall, it is possible that the reactivation of dormant viruses could make things worse when it comes to experiencing COVID-19, although more research is needed at this time.
The authors explain that people often have dormant viruses present in their bodies, and that these viruses can reactivate in certain situations like critical illness. Reactivation of viruses in COVID-19 is an area where there is somewhat limited data.
Researchers used data from the Immunophenotyping Assessment in a COVID-19 Cohort (IMPACC) study. All participants were adults who had confirmed SARS-CoV-2 and experienced hospitalization with COVID-19.
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The research team analyzed data from samples like blood and nasal swabs, looking at some data up to a year after hospital admission. When participants enrolled, they had not received any COVID-19 vaccines. Participants were also divided into categories based on COVID-19 severity.
The researchers found several viruses present in the samples that participants provided. Participants had experienced the reactivation of viruses, especially viruses that were part of the Herpesviridae and Anelloviridae families.
The study authors explain that they chose to focus on viruses from the Herpesviridae and Anelloviridae families because the cohort had a higher prevalence of these viruses.
Overall, they found that about 48% of participants experienced viral reactivation with severe COVID-19. Of these, about two-thirds “had only one virus detected in the acute period.”
The activation of different viruses happened at different times. For example, the human alphaherpesvirus (HSV1) and cytomegalovirus — both viruses implicated in herpes — reactivated around 20 days after participants were admitted to hospitals.
Next, researchers looked at whether detecting reactivated viruses within 40 days of hospital admission was associated with COVID-19 severity. This analysis revealed a number of findings.
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For example, they found that some viruses were linked to COVID-19 severity. When looking specifically at participants classified as critical when it came to COVID-19 severity, those who had detectable nasal levels of Epstein-Barr virus (EBV), HSV1, or cytomegalovirus in any part of the respiratory system were at a higher risk for death within a year.
Additionally, certain viruses were also linked to specific comorbidities and complications. For example, detecting Anelloviridae in peripheral blood mononuclear cells, a type of immune cell, was linked to experiencing shock and admission to the ICU.
Speaking to Medical News Today, study authors Esther Melamed, MD, PhD, and Cole Maguire, PhD, highlighted the following regarding the study:
“We studied over 1,150 hospitalized COVID-19 patients across 20 U.S. hospitals for a year, using sequencing techniques to directly detect when these viruses ‘wake up’ or reactivate. Nearly half of patients had at least one chronic virus reactivate during their illness. This was far more common than previously thought, and it was not limited to people with weakened immune systems. Importantly, many of these patients were otherwise healthy before getting COVID-19.”
Analyses further revealed that reactivation of certain viruses was also linked to certain immune responses in the body.
Researchers identified relationships between Herpesviridae and Anelloviridae reactivation and inflammation. For example, certain viruses were linked to increases in certain inflammatory cytokines.
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The reactivation of certain viruses was also linked to changes in plasma metabolites, which are the products produced from the breakdown process of metabolism.
Finally, they also found that reactivated viruses were linked to certain changes in gene expression.
Next, the researchers looked at how viral reactivation related to long COVID, which is characterized by the continuing experience experience of COVID symptoms for many weeks to months after the initial COVID-19 infection.
One of the major findings was that participants who reported physical disability or fatigue were the most likely to have Anelloviridae in samples from the long-term recovery timeframe.
Melamed and Maguire explained the following:
“We also discovered something new about a lesser-known group of viruses called Anelloviridae. Months after patients left the hospital, those who still had active Anelloviridae were more likely to be experiencing ongoing fatigue and physical disability consistent with Long COVID. This is the first time this virus family has been linked to Long COVID.”
Of note, this study doesn’t establish a causal relationship. For example, it can’t prove that reactivation of dormant viruses causes increases in COVID-19 severity.
Researchers were also possibly limited in their findings by the fact that they studied IMPACC participants, who were not vaccinated and who experienced infection with early SARS-CoV-2 strains. Thus, it remains unclear how people exposed to other strains would be affected.
The authors also note that the choice to use transcripts to look at viral load may have produced certain limitations. Further, the specificity of the collected samples may have influenced the findings, since the researchers only looked at three specific sites, and they only had data on endotracheal aspirate samples in participants who were on ventilators.
Finally, because of the timing of the study, there was no stable definition for long COVID when certain categories were created, so researchers may have been limited in their abilities to look into long COVID and viral reactivation.
Researchers also struggled with participant drop-out.
Microbiology and immunology expert with Johns Hopkins Medicine, Arturo Casadevall, PhD, who was not involved in the study, noted that “the clinical implications at this time are uncertain but it is conceivable that reactivation of other viruses contributes to the disease that we know as COVID-19 and could be promoting the persistent inflammation that is associated with long COVID-19.”
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It is possible that addressing these virus reactivations could help with addressing COVID-19 outcomes.
Jimmy Johannes, MD, a pulmonologist and critical care medicine specialist at MemorialCare Long Beach Medical Center in Long Beach, CA, likewise not involved in the study, noted the following to MNT:
“One possibility is that reactivation of viruses such as EBV, cytomegalovirus, and other chronic viruses could contribute to some of the complications associated with COVID-19, particularly by adding to the inflammatory and immune response. If future studies establish that viral reactivation directly contributes to worse outcomes, it could potentially help doctors identify patients at higher risk for complications or identify new approaches to treatment.”
The findings could also help address ongoing quesrions about long COVID. Melamed and Maguire explained that, “for long COVID, if the Anelloviridae association is confirmed in future studies, it could point toward a new avenue for understanding why some patients develop prolonged symptoms post COVID.“
“It might also open the door to developing targeted therapies for these viruses, which currently have no approved treatments,“ the study authors hoped.
