The awakened threat: how severe COVID-19 can activate dormant viruses

The severe form of COVID-19 can not only cause serious complications during illness, but also "wake up" viruses that have remained inactive in the body for years. This conclusion was reached by scientists who studied the condition of more than a thousand patients hospitalized with coronavirus infection. Some of the reactivated viruses have been linked to the development of long-term effects of COVID-19. About why this discovery attracted the attention of researchers and what it means for patients is in the Izvestia article.

How COVID Wakes up Hidden Viruses

The study focuses on how the severe course of COVID-19 affects viruses already present in the human body. The authors monitored 1,154 adult patients hospitalized with coronavirus infection for a year, regularly analyzing blood samples, nasopharyngeal swabs, and in some patients, samples from the respiratory tract. The work was published in the journal Nature.

During the observation, scientists discovered the reactivation of chronic viruses. The most frequently "awakened" Epstein—Barr virus, cytomegalovirus, herpes simplex virus and representatives of the anellovirus family. At the same time, different viruses were activated at different times: for example, Epstein—Barr virus and anelloviruses were more often detected in the early stages of the disease, while cytomegalovirus and herpes simplex virus were detected later. In addition, each of them was associated with its own changes in the immune system and metabolism.

One of the most unexpected results was that the reactivation of viruses occurred not only in patients with weakened immune systems. The authors concluded that in severe cases of COVID-19, this process is probably primarily associated with a powerful systemic inflammatory response of the body. Thus, the study casts doubt on the previous idea that chronic viruses are activated mainly against the background of severe immunodeficiency.

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Which viruses remain in the body for life

Many viruses do not disappear completely after infection, but enter a so-called latent state. This means that they continue to be in the body, but they do not multiply actively and do not cause symptoms. Under certain conditions — for example, during severe stress, severe illness, or severe inflammation — such viruses can reactivate.

The most common viruses that can persist in the body for decades include the Epstein—Barr virus, which is the cause of infectious mononucleosis. Experts estimate that the majority of adults worldwide are infected with it. Cytomegalovirus and herpes simplex viruses behave in a similar way: after initial infection, they remain in the body for life and usually do not manifest themselves in any way if the immune system successfully controls their activity.

The researchers were particularly interested in anelloviruses. They occur in about 80-90% of the population, but so far there has been no convincing evidence that they themselves cause diseases in humans. That is why scientists have especially carefully studied their behavior after severe COVID-19: if their reactivation is really associated with a deterioration in the condition of patients, this may change the perception of the role of these viruses in medicine.

Why scientists are interested in the long-term COVID

After the completion of the acute phase of infection, some of the study participants continued to experience severe physical limitations. Among the most frequent complaints were severe fatigue and decreased ability to perform normal daily activities, such as dressing yourself or walking for a long time. It was in these patients that researchers more often found persistent activity of anelloviruses.

It is important that we are not talking about the proven cause of the long-term COVID, but only about the discovered connection. The authors emphasize that their work does not allow us to assert that it is the reactivation of anelloviruses that causes long-term symptoms. However, the results show that such viruses can potentially become biomarkers that will help identify patients at increased risk of long-term complications in advance.

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What do the results of the study mean?

The authors of the work believe that their results open up new possibilities for studying long-term COVID and severe viral infections in general. Today, methods of laboratory control of chronic viruses already exist, and antiviral drugs have been developed for some members of the herpesvirus family. In the future, this may help to create new approaches to patient monitoring and risk assessment of complications.

However, the researchers emphasize the limitations of their work. All participants were hospitalized with severe COVID-19, were not vaccinated, and became infected with early variants of the coronavirus. Therefore, it is not yet possible to say that similar processes occur in people with a mild course of the disease, after vaccination or when infected with modern variants of SARS-CoV-2.

The main conclusion of the study is that a severe coronavirus infection can have a more complex effect on the body than previously thought. It not only causes inflammation, but it can also disrupt the delicate balance between humans and viruses that have remained unnoticed for years. To understand whether this knowledge can be used for the prevention and treatment of long-term COVID, scientists will have to conduct new research.