A new study found that COVID-19 can awaken dormant viruses that lie hidden in the body for life, even in people with otherwise healthy immune systems.

Dormant viruses are common, and the ones implicated in this study include the Epstein-Barr virus, which causes mononucleosis and other related viruses in the herpes family. Nearly half of the 1,100 hospitalized patients in the study had at least one such virus reactivate during their illness. Reactivation was more common in sicker patients and was associated with worse outcomes.

The lead author suggested that this could mean COVID does "not always act as a single viral infection and may disrupt the body's internal ecosystem of dormant viruses."

Reactivation occurred in people who were healthy before developing COVID and it wasn't limited to those with suppressed immune systems. This suggests reactivation is more common than previously thought. There is question as to whether studying this reactivation further could help patients with long COVID.

The research team found a viral signal of Anelloviridae, a lesser-known family of chronic viruses, appearing more often in long COVID patients with lasting fatigue and reduced physical function. This provides strong evidence that dormant viruses could contribute to long COVID.