Nikhil Prasad Fact checked by:Thailand Medical News Team Mar 17, 2026 1 hour, 42 minutes ago
Medical News: A large new study from Sweden has uncovered an alarming link between COVID-19 and a higher risk of developing infectious mononucleosis, a condition caused by the Epstein-Barr virus (EBV). What is particularly concerning is that even people with mild COVID-19 appear to face this increased risk, pointing to deeper and longer-lasting effects on the immune system.
Study finds COVID-19 may trigger infectious mononucleosis by weakening immunity
Massive Population Study Reveals Hidden Risk
Researchers from Örebro University in Sweden, including Snieguole Vingeliene, Scott Montgomery, and Ayako Hiyoshi, carried out a nationwide study involving nearly 10 million individuals aged between 3 and 100 years. The study tracked participants from January 2020 to November 2022 using detailed national health records.
Participants were divided into three groups: those who never had COVID-19, those who tested positive but were not hospitalized, and those who required hospital care due to severe COVID-19. The researchers focused on cases of infectious mononucleosis severe enough to require hospital treatment. This illness, often referred to as glandular fever, is caused by EBV and is known for symptoms such as extreme fatigue, fever, sore throat, and swollen lymph nodes.
Strong Link Between COVID-19 and Later Illness
The results showed a clear and consistent pattern. People who had COVID-19 were more likely to later develop infectious mononucleosis compared to those who never had the virus.
Among individuals without COVID-19, about 4.6 cases per 100,000 people occurred annually. This increased to 7.8 per 100,000 among those who had mild COVID-19. For those hospitalized due to COVID-19, the rate rose to 10.5 per 100,000.
After adjusting for age, gender, region, and existing health conditions, the findings remained strong. Individuals with mild COVID-19 had a 61 percent higher risk, while those with severe COVID-19 had nearly six times the risk of developing infectious mononucleosis.
This
Medical News report emphasizes that the consistency of these findings across different groups strengthens the evidence that COVID-19 plays a role in triggering this condition.
How COVID-19 Disrupts the Immune System
Scientists believe the connection lies in how COVID-19 affects the immune system. The virus is known to cause widespread inflammation and can leave lasting changes in immune function for months after infection.
Important immune markers such as interleukin-6 and tumor necrosis factor-alpha remain elevated, while key immune cells may not function normally. These changes can weaken the body’s ability to control other viruses already present in the body. EBV is one such virus. It infects more than 90 percent of people worldwide and remains dormant in the body for life. Under normal conditions, the immune system keeps it under control. However, COVID-19 may disturb this balance, allowing EBV to reactivate a
nd cause infectious mononucleosis.
More Than Just a Temporary Illness
Although infectious mononucleosis is often seen as a short-term illness, it can have long-lasting effects. Many people experience extreme fatigue that can continue for months, affecting their ability to work or study. In some cases, EBV infection has been linked to serious long-term conditions, including multiple sclerosis, autoimmune diseases like lupus and rheumatoid arthritis, and certain cancers such as Hodgkin’s lymphoma.
The researchers caution that their study only included hospital-treated cases, meaning milder infections were not captured. This suggests the true number of cases could be much higher.
Younger Individuals May Be More Vulnerable
A notable finding was that many of those affected were relatively young. This raises concerns that COVID-19 may have a stronger impact on younger immune systems than previously believed.
While the overall risk of severe complications remains low, experts warn that the long-term effects of widespread EBV reactivation following COVID-19 are still unclear and may take years to fully understand.
Conclusions Highlight Long-Term Health Concerns
The findings strongly suggest that COVID-19 can leave lasting effects on the immune system, increasing vulnerability to other infections such as infectious mononucleosis. Even mild infections appear capable of triggering these changes, which may have broader implications for long-term health. This highlights the importance of continued research, monitoring, and awareness, as the full extent of post-COVID immune disruption and its potential role in future chronic diseases is only beginning to emerge.
The study findings were published in the peer reviewed journal: Clinical Infectious Diseases.
https://onlinelibrary.wiley.com/doi/10.1002/jmv.70787
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Read Also:
https://www.thailandmedical.news/articles/coronavirus
https://www.thailandmedical.news/articles/long-covid
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