Could a Viral Infection in Adolescence Lead to MS in Adulthood?

Multiple sclerosis (MS) is an unpredictable disease of the central nervous system (CNS) that affects the brain and spinal cord. According to the National Multiple Sclerosis Society, there were almost 1 million adults living with MS in the United States in 2017, which is more than twice the reported number in 1975.

The common initial symptoms of MS are often vision-related, such as double vision, blurred vision, red-green color distortion, but the disease can affect almost any part of the body, depending on which parts of the CNS are damaged. It can cause balance and muscle weakness, memory and thinking problems, emotional problems and sensations of numbness in areas of the body. 

Multiple sclerosis has both genetic and environmental risk factors, including human leukocyte antigen (HLA) type, infections, low vitamin D levels, higher body mass index (BMI), and smoking, sometimes with potent interactions with HLA risk genes. 

The involvement of infections in increasing the risk of multiple sclerosis has been frequently studied, such as Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), and Chlamydia pneumoniae.

What Causes MS? 

A combination of environmental and genetic factors seems to be responsible for MS, but the exact cause of the disease is unknown. Scientists believe that it is an autoimmune disease. In people with MS, the immune system mistakenly attacks the myelin coating of the CNS.

Myelin protects the nerves and helps messages travel between the brain and the rest of the body. When the protective coating becomes damaged, it can slow, alter, or stop these messages.

Research Studies 

Two meta-analyses found that infectious mononucleosis in adolescents and young adults, a clinical manifestation of EBV infection, more than doubled the multiple sclerosis risk. 

There is also extensive evidence supporting that HHV-6 is associated with increased multiple sclerosis risk. A recent study that collected serum before multiple sclerosis onset suggested that HHV-6A in contrast with HHV-6B, determined serologically, was associated with an increased risk for future multiple sclerosis.

New Study Finds More Evidence 

A new research study recently published in the jornal Brain, found that events that cause inflammation of the CNS can increase the risk of MS diagnosis. The researchers used a large general population-based birth cohort in Sweden to assess the risk of a multiple sclerosis diagnosis from age 20 years associated with hospital-diagnosed infection in adolescence (ages 11-19) and earlier childhood (between birth and 10 years). 

Glandular fever, which occurs due to the Epstein-Barr virus (EBV) and is also known as infectious mononucleosis (IM), showed the greatest association with MS diagnosis. They found that any infection in adolescence increased the risk of multiple sclerosis and remained statistically significant after exclusion of infectious mononucleosis, pneumonia, and CNS infection.

The increased risk of a multiple sclerosis diagnosis associated with viral infection in adolescence was largely explained by infectious mononucleosis. 

According to the researchers these findings suggest that a variety of serious infections in adolescence, including novel evidence for CNS infections, are risk factors for a subsequent multiple sclerosis diagnosis, further demonstrating adolescence is a critical period of susceptibility to environmental exposures that raise the risk of a multiple sclerosis diagnosis.

Sources: 

Anna Guildford, Ph.D (2021, Oct 22) Could viral infections in teenagers lead to MS in adulthood? Medical News Today. Retrieved from:
https://www.medicalnewstoday.com/articles/could-viral-infections-in-teenagers-lead-to-ms-in-adulthood

Xu Y, Smith KA, Hiyoshi A, Piehl F, Olsson T, Montgomery S. Hospital-diagnosed infections before age 20 and risk of a subsequent multiple sclerosis diagnosis. Brain. 2021 Sep 4;144(8):2390-2400. doi: 10.1093/brain/awab100. PMID: 33693538.

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