There is currently no cure for multiple sclerosis (MS), which is a condition that affects around 110,000 people in the UK.
Unpredictable symptoms
The National Multiple Sclerosis Society says the risk of developing MS in the general population is around one in 1000.
MS is a chronic inflammatory disease of the central nervous system that attacks the myelin sheaths protecting neurons in the brain and spinal cord, and its cause remains elusive.
The symptoms are unpredictable and can range from physical disabilities like mobility problems to mental health conditions, such as depression.
Many people with MS report feeling an overwhelming sense of exhaustion, making simple tasks a struggle. In around a quarter of cases, the first noticeable symptom is a problem with one of the patient's eyes, including colour blindness and double vision.
In contrast, Epstein-Barr Virus infection is astoundingly common, and can be found in around 95 per cent of people.
EBV infection can leave people feeling tired and sore, and is also known as mono or herpes. After a person contracts the pathogen, it remains in their system forever, often without any symptoms but occasionally reactivating.
Prof Daniel Davis, professor of immunology at the University of Manchester, who was not involved with the research, said: "Well over 9 in 10 people are infected with this virus worldwide, usually in childhood, and only very rarely does a problem arise.
"We already knew that this virus increases the risk of some cancer types, and now we know that it is also possibly a factor in multiple sclerosis, although it's important to note for most people that have the virus, it will not cause them any problems.
"Crucially, we do not know why only a small fraction of people infected with this virus develop a problem."
He added that other factors will be at play, such as genetics, and a cure may only be found once these have been identified.
The US-based researchers studied the medical records of more than ten million people enlisted in the US military, of which 955 developed multiple sclerosis during their period of service.
Blood samples taken twice a year by the military were analysed by the researchers to determine if the person had the virus, and this was cross-referenced against a later MS diagnosis, which normally only begins to manifest ten years after the identification of EBV.
The risk of a person was found to be 32 times greater in people who tested positive for the herpes virus than in the minority of people who do not have EBV.
A protein and biomarker for nerve degeneration called NfL only increased in those who had been infected with the virus, the researchers write in their study, published in the journal Science.
Their findings cannot be explained by any other known risk factors for MS and suggest EBV may therefore be the leading cause.
Ascherio said: "Currently there is no way to effectively prevent or treat EBV infection, but an EBV vaccine or targeting the virus with EBV-specific antiviral drugs could ultimately prevent or cure MS."
About | Herpes simplex virus
- Most people get HSV-1 (herpes simplex type 1) as an infant or child. This virus can be spread by skin-to-skin contact with an adult who carries the virus. An adult does not have to have sores to spread the virus.
- A person usually gets HSV-2 (herpes simplex type 2) through sexual contact. Herpes simplex viruses spread from person to person through close contact. You can get a herpes simplex virus from touching a herpes sore. Most people, however, get herpes simplex from an infected person who does not have sores. Doctors call this "asymptomatic viral shedding".
- A person with HSV-1 (herpes simplex type 1) can pass it to someone else by: kissing, touching the person's skin, such as pinching a child's cheek, or sharing objects such as silverware, lip balm, or a razor.
- You can get genital herpes after coming into contact with HSV-1 or HSV-2. Most people get genital herpes from HSV-2, which they get during sex. If someone has a cold sore and performs oral sex, this can spread HSV-1 to the genitals — and cause herpes sores on the genitals.
- Once a person becomes infected with a herpes virus, the virus never leaves the body. After the first outbreak, the virus moves from the skin cells to nerve cells. The virus stays in the nerve cells forever. But it usually just stays there. In this stage, the virus is said to be dormant, or asleep. But it can become active again.
