 "Hidden infections could be the missing link in long Covid, says new study")
What if long Covid isn’t caused by Covid-19 alone? A new scientific review suggests that lingering symptoms may be fuelled by hidden infections already present in the body, quietly reawakening after the immune system is disrupted by Covid-19.
The study, “The role of co-infection in the pathogenesis of acute SARS-CoV-2 infection and development of post-acute sequelae”, was published in the journal eLife.
For millions around the world still struggling with breathlessness, extreme tiredness and “brain fog”, this fresh perspective could open new avenues for understanding and ultimately treating long Covid.
What Is Long Covid?
Long Covid, also called post-Covid-19 condition or PASC, refers to symptoms that continue or appear weeks to months after the initial infection. These can include:
- Persistent fatigue
- Cognitive issues such as difficulty concentrating
- Shortness of breath
- Muscle and joint pain
- Sleep problems
Despite affecting millions globally, its exact biological causes remain poorly understood. ALSO READ | Air pollution in India biggest health crisis since Covid, warn doctors
When other pathogens enter the picture
Researchers from multiple institutions, including Rutgers Health, reviewed existing evidence and suggest that long Covid may not be driven by SARS-CoV-2 alone. Instead, dormant infections already present in the body may be reactivated or unmasked when Covid-19 disrupts the immune system, contributing to persistent symptoms.
The researchers argue that when immune balance is disturbed, other viruses and bacteria can resurface or gain a foothold, prolonging illness even after the initial COVID-19 infection has resolved. They highlight three broad ways this may happen:
Acute co-infections - These occur at the same time as active Covid-19 and include respiratory or other infections such as influenza, respiratory syncytial virus (RSV), measles, adenovirus, streptococci and more.
Chronic infections and co-infections - Conditions such as human immunodeficiency virus (HIV), cytomegalovirus (CMV) and tuberculosis may persist alongside Covid, placing ongoing strain on the immune system and potentially worsening recovery.
Reactivation of latent infections - Some infections lie dormant in the body for years. When Covid disrupts immune regulation, viruses such as Epstein-Barr virus (EBV), varicella zoster virus (VZV) or latent tuberculosis may reactivate, prolonging symptoms well beyond the acute illness.
- Epstein-Barr Virus (EBV) - The study notes that around two-thirds of people with long Covid showed signs of recent EBV reactivation. EBV is extremely common and typically infects people early in life, remaining inactive without causing symptoms. Following Covid-19, however, weakened immune surveillance may allow the virus to resurface, contributing to fatigue, brain fog and other lingering complaints.
- Tuberculosis (TB) - An estimated one-quarter of the world’s population carries latent tuberculosis. Under normal conditions, the immune system keeps the bacteria in check. Researchers suggest that Covid-19-related immune disruption may allow latent TB to reactivate in some individuals, potentially adding to the symptom burden seen in long Covid.
What this means for patients
The review highlights several important points:
- Co-infections may worsen or prolong symptoms when they occur before, during, or after Covid-19
- The theory of “immunity theft” suggests that Covid-19 might weaken immune defences, leaving the body more vulnerable to other pathogens.
- If these infections are contributing to long Covid, existing antiviral or antibiotic medications might help, but this remains to be tested.
Limitations and next steps
The review does not prove that hidden infections cause long Covid, only that the links are plausible and merit further study.
"Everyone has heard it a million times, but it bears repeating: Correlation doesn't equal causation," said Maria Laura Gennaro, microbiologist at Rutgers New Jersey Medical School and chair of the NIH RECOVER Microbiology Task Force studying long Covid.
While the researchers hope their work will open new lines of investigation, large population studies, animal models and clinical trials will be needed to establish cause and effect.
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This report is for informational purposes only and is not a substitute for professional medical advice.