More evidence about the role of EBV infection in the development of MS

At the moment, we don’t know for sure why people develop MS. It’s likely to be due to a mix of genes, something in your environment, and some lifestyle factors. 

Previous research found a link between EBV infection and MS. EBV is a virus which infects about 95% of people and remains as a lifelong infection. Most people don’t know they’ve been infected but for some people, EBV causes glandular fever.  

Some studies suggest EBV infection may actually play a role in causing someone to develop MS. But proving a causal relationship is very difficult. For example, it could be that MS actually makes you more likely to become infected with EBV rather than the other way round.  

A new study by Professor Alberto Ascherio and colleagues has added some new evidence to support the idea that EBV could be a cause of MS.  

What was the study? 

The researchers followed more than 10 million young adults from the US military. Over 20 years, they tracked the relationship between new EBV infections and the onset of MS.  

Such a large, long-term study is very valuable. Because EBV is so common, we need to look at a huge number of people to find those who haven’t been infected by EBV yet.  

Tracking EBV infections and MS development over a long period of time means we can see if there’s evidence the EBV infection comes first. That’s really important for proving causality.  

At the start of the study, the team took blood samples to see if people were infected with EBV. They then took samples every two years so they could see who became infected with EBV and when. They also analysed the blood samples for a marker of nerve damage that could be an early sign of MS seen in the years before diagnosis.  

What did they find? 

Out of 801 people who developed MS, only one person never tested positive for EBV during the study. But most people had already been infected with EBV before the beginning of the study.

So the researchers looked at the 142 people not yet infected with EBV (35 who developed MS and 107 who didn’t). 97% of the people who developed MS became EBV positive. In comparison, only 57% of people who didn’t develop MS became EBV positive. 

The risk of developing MS increased 32-fold after EBV infection. But other infections, like a virus called cytomegalovirus, didn’t show the same increased risk for developing MS. 

A key new finding is the increase in the marker of nerve damage seen in people who developed MS. Crucially, this was only seen after they became EBV positive.  

According to the researchers, their findings can’t be explained by any other known risk factor for developing MS. 

What do these findings mean for people with MS? 

These results provide good evidence that the EBV infection does happen before MS starts to develop – even the very early stages of MS before a diagnosis.  

But most people who are infected with EBV don’t go on to develop MS. So even if EBV is usually required to trigger MS, it can’t be enough to cause it by itself. We need to deepen our understanding of how EBV interacts with other risk factors like vitamin D and genes.  

Importantly, to be sure EBV is definitely causing MS, we need to see what impact preventing EBV infection has on MS rates. And for that, we first need an effective vaccine to prevent EBV.  

Research into EBV vaccines is underway, but it’s still at a very early stage. Last week, the first person joined a phase 1 clinical trial of a potential EBV vaccine. This is using the same mRNA technology as some COVID-19 vaccines.  

So we’re making progress. But it will be many years before we can find out whether preventing EBV infection could stop people developing MS. 

What is the MS Society doing? 

We’ve been interested in the role of EBV in MS for many years. We've supported several researchers doing projects in the area, including:

• Exploring the biological processes that could be involved in EBV as a cause of MS
• Exploring an antiviral treatment that may have the potential to target EBV

We know preventing MS is a top priority for people affected by MS, so it’s great to see research in the area building momentum. Now we need researchers and funders from different countries to come together to drive forward research into MS prevention.  

Read the full study on the journal website

Read about the phase 1 EBV vaccine trial