COVID-19 Can Wake Up Dormant Viruses Already in the Body
Most people carry a handful of viral stowaways they never think about. Epstein-Barr, cytomegalovirus, and other members of the herpesvirus family infect the vast majority of people at some point in childhood or adolescence and are never fully cleared. Instead, they go quiet, tucked away in reservoirs of cells, kept dormant by a functioning immune system for the rest of a person’s life. A large new study shows that a severe bout of COVID-19 can be enough to wake several of them up at once.
The Largest Study of Its Kind
The research, published in Nature and led by scientists at Dell Medical School at the University of Texas at Austin, followed more than 1,100 people hospitalized with COVID-19, drawing on data from the Immunophenotyping Assessment in a COVID-19 Cohort, a National Institutes of Health funded consortium spanning more than 15 research institutions and 20 hospitals across the United States. The team collected more than 200,000 samples and generated over a billion data points over the course of a year, tracking which viruses reactivated, when, and in whom.
Nearly half of the patients studied had at least one dormant virus reactivate at some point during their COVID-19 illness. Reactivation was more common among sicker patients and was associated with longer hospital stays, a wider range of complications, and higher mortality.
A Surprise for Healthy Immune Systems
Doctors have long known that dormant viruses can reawaken in people whose immune systems are suppressed, such as transplant recipients or cancer patients undergoing chemotherapy. What surprised the research team was how often reactivation showed up in people who had been perfectly healthy before catching COVID-19.
“This finding suggests that COVID-19 may not always act as a single viral infection and may disrupt the body’s internal ecosystem of dormant viruses, creating a state of dysvirosis,” said lead author Cole Maguire, who carried out the research as a doctoral student in the UT Interdisciplinary Neuroscience Program under Dr. Esther Melamed, and is now a second-year medical student at Dell Medical School.
The pattern held even in patients without any obvious immune suppression, suggesting that severe illness and inflammation alone, not just a weakened immune system, may be enough to loosen the body’s grip on these long-term viral tenants.
A Possible Piece of the Long COVID Puzzle
The study also turned up a notable connection to long COVID, the cluster of lingering symptoms, including fatigue, cognitive difficulties, and reduced physical function, that can persist for months or years after the initial infection clears and currently has no approved treatment.
Patients who developed long COVID with lasting fatigue and reduced physical function showed a stronger signal of reactivated anelloviruses, a family of viruses that is common but still poorly understood. The study cannot prove that viral reactivation causes long COVID, since it only shows an association rather than a direct causal link, but researchers say the connection is strong enough to warrant closer investigation.
Why Herpesviruses in Particular Matter
Among the viruses studied, the herpesvirus family drew particular attention. Epstein-Barr virus, best known for causing mononucleosis, and cytomegalovirus, which can produce flu-like symptoms, both showed patterns of reactivation tied to more severe COVID-19 outcomes.
Unlike anelloviruses, herpesviruses already have established diagnostic tests and existing antiviral treatments, which raises a practical possibility. “Our findings have important implications for patient care. Tests already exist for several of the chronic viruses studied, and some viruses in the herpes family can be treated with existing antiviral drugs,” said Dr. Melamed, the study’s principal investigator and an assistant professor of neurology at Dell Medical School. “The next step is determining whether identifying and treating reactivated viruses can improve outcomes for patients with acute COVID-19 and long COVID.”
What the Findings Do Not Yet Show
The patients in this study were hospitalized, unvaccinated, and largely infected earlier in the pandemic, so it remains unclear whether the same reactivation patterns hold up against current variants and in populations with widespread vaccination and prior immunity. Researchers say more work is needed to determine whether the same disruption occurs in milder, non-hospitalized cases.
Even with those open questions, the study adds a new dimension to how COVID-19’s effects on the body are understood, suggesting that some of its most serious consequences may come not just from the virus itself, but from the dormant infections it stirs awake along the way.
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