Genital herpes has been linked to brain shrinkage, which suggests the infection could increase the risk of cognitive decline and even Alzheimer’s disease.
at Columbia University in New York and his colleagues analysed the MRI brain scans and blood test results of 455 adults, aged 70 on average, who took part in a long-term health-tracking study in Manhattan.
Those who tested positive for herpes simplex virus 2 (HSV-2) – the sexually transmitted infection that causes genital herpes – tended to have reduced thickness of their cerebral cortex, the outermost brain layer, which orchestrates important functions such as memory, perception and language. This association persisted after accounting for factors such as the participants’ level of education and whether they smoked.
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“Thinning of the cortex is not what you want to see, as it’s generally the beginning of cognitive decline and increases the risk of Alzheimer’s disease,” says at St Vincent’s Hospital in Sydney, Australia, who was not involved in the study.
The results don’t prove that an HSV-2 infection causes brain degeneration, only that there is an association, but they do reinforce findings from other studies, says Vissel. For example, a previous analysis of the same Manhattan group found that those who tested positive for HSV-2, along with several other viruses, .
Other members of the herpes virus family, including herpes simplex virus 1 (HSV-1), which causes cold sores, and varicella-zoster virus, which causes chickenpox and shingles, . Furthermore, “mini-brains” grown in the lab and infected with HSV-1 develop beta-amyloid plaques, hallmarks of the condition.
Herpes viruses burrow into nerves that connect to the brain and stay there for life, so it makes sense that their “ongoing infection of the nervous system would have consequences”, says Vissel. “I think an increasing proportion of the scientific community is now open to the idea that some forms of dementia may be related to infections, particularly herpes.”
If confirmed in further research, vaccines that prevent herpes viruses may help to protect our brains, he says. It has already been shown that the and the same may be true of HSV-2 vaccines that are being developed, says Vissel.
The HSV-2 vaccine that is furthest along in development is an mRNA vaccine made by BioNTech that entered clinical trials in late 2022, but the results aren’t available yet.
Journal of the Neurological Sciences
