The herpes virus can travel to the brain during oral sex, scientists warn.

Research has shown that individuals can contract herpes simplex virus type 1 (HSV-1) in and around the nose, creating a direct pathway to the brain that poses significant risks.

The infection, in theory, could then cause inflammation and lead to complications such as brain damage and dementia.

The University of Chicago’s Professor Deepak Shukla, who led the research, told DailyMail.com this mode of transmission could occur in the bedroom.

Experts have highlighted that any scenario allowing a person’s nose to encounter HSV-1 particles from an individual shedding the virus can lead to transmission.

Nearly four billion people worldwide carry HSV-1, the main cause of oral herpes.

The most common way it’s transmitted from a carrier to someone without herpes is by touching an active sore.

In the case of someone with oral herpes, known for causing cold sores around the lips, the risk involves coming into contact with the person’s cold sore or saliva when they are actively shedding the virus.

Professor Deepak Shukla explained that one of the possible ways someone could contract a herpes infection through the nose is through oral sex on an infected partner (stock image)

However, there are cases of HSV-1 causing genital herpes, meaning that an infected carrier passed on the virus during oral sex.

Essentially, someone could inhale infectious particles when their face is pressed up against skin or sores shedding HSV-1.

For the first time, in the journal mBio, Professor Shukla revealed that there’s a key enzyme in the human body that could make these herpes infections entering through the nose particularly devastating for brain health.

The enzyme is called heparanase (HPSE) and experiments revealed that it might be a hidden puppet master, amplifying inflammation and driving the long-term brain damage after HSV-1 sneaks into the brain through the nose.

HPSE is a normal enzyme in humans and other mammals, which breaks down sugar-like molecules that are part of the supportive structures of our cells.

HPSE usually acts like a cleanup crew, clearing out damaged cells so the body can regenerate injured tissues.

However, when someone becomes infected with HSV-1, the herpes virus hijacks this enzyme and causes it to produce too much inflammation. 

For most of the world’s population that carries HSV-1 with only the occasional cold sore, there really isn’t much to worry about.

When this infection somehow reaches the brain, however, HSV-1 can cause encephalitis, a dangerous brain inflammation, or linger quietly, possibly contributing to conditions like Alzheimer’s disease later in life.

Overall, cases of herpes simplex encephalitis (HSE), where HSV-1 infects the brain, causing inflammation, are still rare. 

In fact, HSE occurs in about two to four cases for every million people with the virus. However, Dr. Shukla told DailyMail.com that he believes the number of unreported nasal herpes cases is much higher. 

The new study discovered a key enzyme that appears to make HSV-1 infections worse, leading to severe brain inflammation when the virus reaches the brain on rare occasions

Using mice that had HSV-1 dripped into their noses, Shukla’s team found that animals with normal levels of HPSE suffered from more severe herpes infections, died faster, and had worse symptoms like nasal swelling and breathing problems.

After an autopsy, scientists discovered the mice with normal HPSE levels had more dead cells in their brains, more inflammation, and more immune cells (microglia) in the olfactory bulb – the brain’s smell center and entry point from the nose.

‘There is definitely nerve damage if you take the intranasal route, and the effects are long-term, which is alarming,’ Shukla noted in a statement.

The herpes-infected mice with normal HPSE levels also displayed concerning behavioral changes while they were still alive.

The mice suffered from memory loss, showed more signs of anxiety, and lost their balance more often while walking. These symptoms appeared in less than six months.

When Shukla’s team conducted these same experiments using mice that had been genetically engineered to produce less HPSE, the viral infection did significantly less damage to the brain.

The researchers noted that this seems to prove that herpes uses the enzyme to turbocharge harmful inflammation. When this takes place in the brain, it could be fatal for someone with HSV-1.

Making matters worse, there is no cure for HSV-1 or HSV-2 (the main cause of genital herpes during sex).

As for what this could mean for human patients, Prof. Shukla said that the effects on people infected with herpes through the nose would likely vary greatly from person to person.

Specifically, the symptoms would likely develop more slowly in people than in mice and their severity would depend on the strength of each person’s immune system and how often they have herpes flareups.

‘Our findings serve as a warning that unchecked herpes can lead to significant behavioral abnormalities, motor function issues, and coordination problems over time,’ Shukla told DailyMail.com.