Covid-19 Can Reawaken Dormant Viruses in the Body, Which Might Worsen Symptoms of the Respiratory Illness, Study Suggests

Most people become infected with a virus at some point in their lives, be it one that causes the flu or one that causes the common cold. Usually, our bodies can fully clear them out. But some stick around, sleeping in the body until something reawakens them.

The herpesvirus that causes chickenpox, for instance, can later lead to shingles. Now, researchers have found that Covid-19 might be one of those triggers. Out of more than 1,000 unvaccinated patients who were hospitalized with the respiratory illness, nearly half experienced a reactivation of dormant viruses, and some were associated with more severe Covid-19 or long Covid.

The findings, published in the journal Nature on August 5, provide a better understanding of the connections and could help pave the way for new medicines. Researchers have noticed some links between Covid-19 and certain viruses that stay in the body. Those include connections with cytomegalovirus (CMV), which can cause flu-like symptoms, and the Epstein-Barr virus, which causes mononucleosis—the “kissing disease”—and is associated with some cancers and autoimmune diseases.

Both are herpesviruses, a common class of viruses that most people worldwide are carrying, even without symptoms. Past research on Covid-19 and viral reactivation has involved relatively few participants. So Melamed and colleagues examined 1,154 unvaccinated patients hospitalized with Covid-19 between May 2020 and March 2021.

They had provided nasal swabs, blood samples and lung fluids during their hospital stays and for the following 12 months. There have been more than 779 million reported cases of Covid-19 reported worldwide, according to the World Health Organization. Analyses identified 11 reactivated viruses among nearly half the participants within 40 days of hospital admission.

Some of the most common were CMV, Epstein-Barr virus and Herpes simplex virus type 1 (HSV1), which causes cold sores, although they followed different timelines. Epstein-Barr virus generally peaked early on, while CMV and HSV1 appeared about three weeks later. Additionally, anelloviruses—widespread viruses that are typically considered harmless—showed up around the time of hospital admission and declined several weeks later.