A new study suggests that severe COVID-19 infection could reactivate dormant viruses that remain in the body following earlier illnesses.
The study, published in the journal Nature, involved 1,154 patients hospitalised with COVID-19 and was conducted by researchers at Boston Children’s Hospital along with collaborators from more than 20 biomedical research centres across the US and Ontario, Canada. Over the course of a year, the team examined more than 200,000 biological samples collected from the patients, ABC News reported Monday (local time).
What did the study find?
The researchers found that 11 types of dormant viruses were reactivated within the first 40 days after patients were admitted to hospital with SARS-CoV-2, the virus responsible for COVID-19. These included several herpesviruses, such as Epstein-Barr virus, cytomegalovirus and herpes simplex virus-1, as well as viruses from the Anelloviridae family, which has not been definitively linked to any disease in humans.
According to the study, while these viruses are usually inactive but present in healthy individuals, they can reactivate during periods of illness or stress. It also found that the reactivation of Anelloviridae, a virus carried by most adults, was associated with long-term physical disability and long COVID, a condition in which symptoms persist for at least four weeks after the initial infection.
The researchers also found that two herpes viruses, Epstein-Barr virus and cytomegalovirus, appeared to become active in response to inflammation rather than weakened immune function, pointing to a previously unidentified mechanism through which viruses may reactivate during severe illness.
Researchers explain study findings
Expressing surprise at the study's findings, Dr. Ofer Levy, a study co-author and director of the Precision Vaccines Program at Boston Children's Hospital, said, "It was not previously known to this degree of detail and scale how viral reactivation (i.e. the "waking up" and replication of non-SARS-CoV-2 viruses that live in our body -- such as herpes viruses) might associate with COVID severity and outcome."
Levy said the findings raise the possibility that the reactivation of other viruses may also play a role in COVID-19 illness, although further research is needed to confirm the link.
Dr. William Schaffner, who was involved in the study and is a professor of preventive medicine at Vanderbilt University Medical Center in Nashville, said the new study raises more questions than it answers, adding that further research is needed to determine if the results are noteworthy. Schaffner said, "The authors carefully do NOT attribute any disease (including long COVID) to [the reactivated viruses]," and added, "It is not clear whether they play any role in disease production; this may be an entirely coincidental event."
Although the COVID-19 pandemic is over, SARS-CoV-2, the virus responsible, continues to cause infections with both acute and long-term consequences, Levy said, adding that it is estimated that up to 50,000 Americans died from COVID-19 between 2025 and 2026, while as many as 10 million Americans may have experienced long COVID during the preceding year.
