Virus most people have had ‘can change your behaviour’ if it hits the mind, specialists discover

Since it is so common, and mostly harmless, scientists say HSV-1 has gone “underdiagnosed and understudied,” but the consequences could be much more severe than once thought

A virus that most humans have in their system can cause behavioural changes if it finds one sneaky route into the brain, according to new research.

Herpes simplex virus type 1 (HSV-1) is usually associated with cold sores, and the World Health Organization (WHO) estimates that 64% of the global population under the age of 50 is infected. Most people will go for extended periods of time without symptoms, or symptoms may never even present themselves.

Since it is so common, and mostly harmless, scientists say HSV-1 has gone “underdiagnosed and understudied,” but the consequences could be much more severe than once thought.

Recent studies have found a link between herpesviruses and neurodegenerative disease. Scientists have also discovered that the virus embeds for life in our peripheral nervous system. Terrifyingly, the virus can travel to the brain and lead to severe behavioural changes.

Lead author of the study Dr Deepak Shukla of the University of Illinois Chicago said: “If an infected individual is shedding virus via tears, it could reach the nasal cavity, where it could go more directly to the brain.

“The neurological consequences, we believe, are much more severe than you would normally see with fever blisters or ocular infection.”

Shukla’s study infected mice with HSV-1 and observed them for six months, equivalent to several human years.

The team observed signs of neuronal damage and inflammation, and over time they performed worse on memory and coordination tests.

Shukla added: “There is definitely nerve damage if you take the intranasal route, and the effects are long-term, which is alarming.”

However, it’s not all doom and gloom. Previous research indicated that HSV-1 might make use of a certain enzyme in our cells to help it invade brain cells successfully. Mice with the a specific gene knocked out did not see the same neurological issues, which could indicate a potential therapeutic avenue to prevent these damaging effects.

Scientists are continuing to research the link between HSV-1 and neurological issues. While this particular pathway to the brain is rare in humans, the authors are concerned about the potential for harm given it’s such a direct route.

These findings in mice may not directly apply to humans, but the team say their results are a basis for future research that could reveal the scale of this potential issue in humans, as well as how to tackle it.

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