Nature: Study links severe COVID-19 to reactivation of dormant viruses

A severe case of COVID-19 may trigger the reactivation of dormant viruses already present in the body, potentially worsening illness and increasing the risk of developing long COVID, according to a new study published in the journal Nature.

The research, which analysed more than 1,000 people hospitalised with COVID-19 during 2020 and early 2021, found that nearly half experienced a reactivation of previously dormant viruses. The phenomenon was associated with more severe cases of COVID-19 and a higher likelihood of long-term symptoms.

Researchers say the findings could eventually lead to new treatment strategies if future studies confirm that reactivated viruses contribute directly to severe disease and long COVID.

"COVID probably induces the stress that triggers the reactivations, and then these reactivations further amplify the inflammation," said Esther Melamed, a physician-scientist at the University of Texas at Austin and a co-author of the study. "COVID is not really acting on its own."

Many viruses acquired during childhood remain dormant in the body for life, normally kept under control by a healthy immune system. The study found that common viruses such as Epstein-Barr virus, cytomegalovirus, herpes simplex virus and anelloviruses were among those that became active again during severe COVID-19.

Researchers observed that the viruses reactivated at different stages of infection rather than simultaneously. Epstein-Barr virus and anelloviruses typically became active early in the course of COVID-19, while cytomegalovirus and herpes simplex virus tended to reactivate about three weeks later, primarily in the respiratory system.

The findings also challenge the assumption that dormant viruses only reactivate in people with weakened immune systems.

"The most striking" finding is that virus reactivation occurred even in patients with otherwise healthy immune systems, said Resia Pretorius, a physiologist at Stellenbosch University in South Africa, who was not part of the research team.

According to the study, patients receiving immunosuppressive medication during their hospital stay were no more likely to experience viral reactivation than those who were not taking such drugs, suggesting that the stress caused by severe COVID-19 alone may be enough to overwhelm the immune system.

The researchers say further studies are needed to determine whether treating reactivated viruses could reduce the severity of COVID-19 or help prevent long COVID.

By Sabina Mammadli