Severe COVID-19 reawakens up to 11 dormant viruses in hospitalized patients, with a little-known family called Anelloviridae showing the strongest link to lasting physical disability and long COVID, according to a large biomarker study published in the journal Nature. Researchers at 20 U.S. hospitals tracked 1,154 patients under a project funded by the National Institutes of Health, discovering that strong bodily inflammation rather than weakened immunity triggers these latent infections to return.
Anelloviruses and Long COVID Risk
About 90 percent of people carry anelloviruses without experiencing symptoms or obvious harm. According to Dr. Ofer Levy, a physician and researcher at Boston Children’s Hospital and site principal investigator on the work, these little-known pathogens have emerged as an unlikely suspect in long COVID. Researchers still know little about what these viruses do when active, but the new data links them closely to chronic post-viral conditions. “This association with long COVID is an interesting finding as millions around the world suffer from this chronic condition,” Dr. Levy said. Joann Diray Arce, who leads the study’s clinical and data coordinating center at Boston Children’s Hospital, noted that the team followed more than one thousand patients, collected over 200,000 samples, and generated more than 1 billion data points over a year.
Did you know? Anelloviruses belong to a family so poorly understood that researchers are only now exploring whether they actively contribute to disease or simply arrive alongside post-viral illness.
Inflammation Triggers Dormant Infections
Doctors typically view viral reactivation as a clear marker of a suppressed immune system. Conditions like untreated HIV, chemotherapy, and transplant drugs routinely allow old infections to return. However, Dr. Levy’s team found that Epstein-Barr and cytomegalovirus reactivated in patients whose immune defenses appeared to be functioning normally. Those specific patients experienced severe systemic inflammation. The research team concluded that rampant inflammation acts as the primary switch waking these dormant pathogens, turning standard medical assumptions upside down. “Traditionally, viral reactivation is most associated with weakened immunity/immunocompromise. Here we noted viral reactivation in the context of strong inflammatory responses which is more unusual and might reflect distinct aspects of long COVID pathophysiology,” Dr. Levy told Earth.com.
The Scale of Post-COVID Complications
Public attention has largely shifted away from the pandemic, but the clinical reality remains stark. According to Dr. Levy, up to 50,000 Americans died of COVID during the 2025-2026 respiratory season, while estimates suggest over 10 million U.S. adults currently suffer from long COVID. The NIH-backed study analyzed genetic material from patient blood samples within 40 days of hospital admission. Researchers tracked 11 reawakened viruses, noting that Epstein-Barr, herpes simplex 1, cytomegalovirus, and anelloviruses appeared most frequently. Because the project focused exclusively on patients sick enough to be admitted to a hospital, mild cases managed at home remain outside this specific dataset.
Pro Tip: Clinicians tracking post-viral syndromes are beginning to evaluate whether identifying specific reawakened pathogens can help anticipate upcoming medical complications in recovering patients.
Future Diagnostics and Antiviral Treatments
The research team is currently investigating how the human immune system responds to these pathogens throughout the timeline of a coronavirus infection. Scientists aim to pinpoint precise treatments that can suppress reactivated viruses and establish optimal intervention windows. “Having new insight as to the molecular and viral associations with long COVID could point the way to better understanding and ultimately better diagnostics and treatments,” Dr. Levy said. If follow-up studies confirm that anelloviruses directly contribute to chronic illness, researchers suggest that developing specific antivirals against the virus family may become a viable clinical strategy.
Frequently Asked Questions
What are anelloviruses?
Anelloviruses are a little-known family of viruses carried by roughly 90 percent of people, typically without causing any symptoms or health problems.
What triggers dormant viruses to reawaken during COVID-19?
According to Boston Children’s Hospital researchers, severe bodily inflammation rather than a suppressed immune system triggers the reactivation of dormant viruses in hospitalized COVID-19 patients.
Are mild COVID-19 cases included in the Nature study?
No. The study tracked 1,154 patients who were sick enough to be admitted to one of 20 participating U.S. hospitals, meaning individuals with mild infections managed at home were not included.
Can doctors treat these reactivated viruses?
Researchers are currently working to identify treatments that can control reactivated viruses and determine the precise timing required for effective medical interventions.
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