Why some people don't fully recover from COVID: Study links infection to dormant virus reactivation

For years, researchers have suspected that COVID-19 does more than trigger a respiratory infection. Many patients recovering from the virus have reported lingering fatigue, brain fog and other unexplained symptoms long after the initial illness.

Now, one of the largest studies to date has strengthened a controversial theory: COVID-19 may awaken viruses that have been lying dormant inside the body for years.  

The findings do not suggest that everyone who contracts COVID-19 will experience viral reactivation. Instead, they indicate that SARS-CoV-2 infection can disrupt the immune system in ways that allow certain latent viruses to become active again, potentially contributing to prolonged illness in some people.  

What are dormant viruses?  

Several viruses can remain inside the human body for life after the initial infection. Rather than disappearing completely, they enter a dormant or "latent" state, where they remain inactive and are kept under control by the immune system.

Some of the best-known examples include:  

• Epstein-Barr virus (EBV): Causes infectious mononucleosis and infects most adults worldwide.
• Cytomegalovirus (CMV): A common herpesvirus that usually remains harmless in healthy individuals.
• Human herpesvirus-6 (HHV-6): Often contracted during childhood before becoming dormant.
• Varicella-zoster virus: The virus responsible for chickenpox that can later reactivate as shingles.  

These viruses can reactivate when the immune system is weakened by illness, stress or certain medications.  

What did the new study find?  

Researchers analysed biological data from a large group of people and found strong evidence that COVID-19 infection is associated with the reactivation of multiple latent viruses, particularly members of the herpesvirus family.  

The study provides some of the clearest population-level evidence yet that viral reactivation is not an isolated phenomenon but may occur in a significant proportion of COVID-19 patients.  

Scientists say this could help explain why some people continue experiencing symptoms weeks or even months after recovering from the acute infection.  

Why does this matter for Long COVID?  

Long COVID remains one of the biggest medical mysteries of the pandemic. While no single mechanism explains every case, researchers increasingly believe it may result from several overlapping biological processes.  

One of those mechanisms is viral reactivation. If dormant viruses become active again, they could trigger chronic inflammation, alter immune responses and contribute to symptoms such as:  

• Persistent fatigue  
• Brain fog and memory problems  
• Muscle aches  
• Sleep disturbances  
• Swollen lymph nodes  
• General malaise  

The new findings add weight to this hypothesis but do not prove that reactivated viruses are the sole cause of Long COVID. Scientists believe they are likely one piece of a much more complex puzzle.  

Why would COVID-19 wake up these viruses?

Researchers believe SARS-CoV-2 can temporarily disrupt normal immune surveillance. Under healthy conditions, the immune system continuously suppresses latent viruses. During COVID-19, however, immune cells may become depleted or dysregulated, reducing their ability to keep these dormant infections in check.  

Once that balance is disturbed, latent viruses may begin replicating again before the immune system regains control. Scientists are still investigating exactly how this process unfolds and why it appears to affect some individuals much more than others.  

Does this happen to everyone? No. Most people infected with COVID-19 recover without developing Long COVID or experiencing clinically significant viral reactivation.  

Researchers say factors such as age, immune health, underlying medical conditions, genetics and the severity of the initial infection may all influence whether dormant viruses become active again.  

Further studies are needed to determine who is most at risk and whether viral reactivation directly causes symptoms or simply serves as a biological marker of immune disruption.  

Could this change treatment?  

Potentially, but not immediately. The findings open the possibility that future treatments for some Long COVID patients could include therapies targeting latent viruses alongside approaches that regulate immune function.  

However, experts caution that the research does not mean antiviral drugs should routinely be prescribed for people recovering from COVID-19. Clinical trials will be needed to determine whether treating reactivated viruses actually improves patient outcomes. The study provides compelling evidence that COVID-19 can disturb the immune system enough to reactivate viruses that have remained dormant in the body for years.