It has been found that COVID-19 awakened other viruses hiding in the body. These were also linked to more severe COVID-19 symptoms and longer-lasting side effects. If future research confirms a causal relationship, antiviral drugs that target other viruses may help treat COVID-19 aftereffects.
A research team led by Esther Melamed, a neurology professor at the University of Texas, tracked 1,154 COVID-19 patients hospitalized at 20 U.S. hospitals from May 2020 to Mar. 2021 for one year and collected and analyzed biospecimens. The study found that during the infection period, nearly half of the patients had one or more dormant viruses in the body resume activity. The results were published on the 6th in the international journal Nature.
◇ Dormant viruses awaken at different times
A representative example of reactivation after COVID-19 infection is the Epstein-Barr virus (EBV). It is a common herpesvirus that almost everyone around the world is infected with at least once, and healthy people usually show no particular symptoms even if infected. But among COVID-19 patients, when this virus reactivated, COVID-19 symptoms became more severe.
The same was true for other herpesviruses such as cytomegalovirus (CMV) and herpes simplex virus, as well as the Anelloviridae family. Melamed said, "COVID-19 appears to cause stress that triggers viral reactivation, and in turn these viruses seem to further amplify inflammation caused by COVID-19," adding, "In reality, COVID-19 did not occur due to a single virus alone."
Until now, the reawakening of viruses latent in the body was thought to occur only in people whose immunity had dropped significantly, such as those with HIV. But most COVID-19 patients whose dormant viruses reawakened this time had no immune problems before infection.
Some patients received immunosuppressants in the hospital for other conditions, but that did not increase the likelihood of viral reactivation compared with others. The team said this suggests that stress from COVID-19 alone can overload the immune system enough to wake dormant viruses.
COVID-19 also did not wake all latent viruses in the body at once. Epstein-Barr virus and anelloviruses surged early after COVID-19 onset and peaked right after admission. In contrast, cytomegalovirus and herpes simplex virus mainly appeared in the respiratory tract three weeks after infection.
◇ Suspect viruses for long COVID also identified
The study also found clues for treating chronic COVID-19 syndrome, known as long COVID, in which COVID-19 symptoms persist. Long COVID refers to symptoms lasting more than three months after a COVID-19 diagnosis. People commonly feel mental fogginess as if a cloud is over the brain and have memory loss. Neurological symptoms such as loss of taste or smell, fatigue, and dizziness are also included. According to the World Health Organization (WHO), about 1 in 10 COVID-19 patients develop long COVID, but its cause still has not been clearly identified.
Among the reawakened viruses in this study, anelloviruses were linked to long COVID symptoms. The researchers noted that when reactivated anelloviruses were found in patient samples, certain white blood cells were more active. Melamed said, "Anelloviruses may not be passive bystanders but could actually contribute to immune dysregulation," adding, "We need to see whether suppressing this virus treats long COVID."
David Putrino of the Icahn School of Medicine at Mount Sinai in New York said, "The fact that SARS-CoV-2, the virus that causes COVID-19, mediates the reactivation of other viruses could lead to new treatments." That suggests existing antivirals could be used to treat long COVID. Putrino's team has already begun a phase 2 clinical trial using antivirals that target herpesviruses in long COVID patients.
References
Nature (2026), DOI: https://doi.org/10.1038/s41586-026-10740-z