You’re not feeling too hot. You’ve had cold and flu symptoms over the last few days, and suddenly those pesky blisters re-appear around your lips: cold sores. While the name might imply it’s the result of that nasty cold, cold sores stem from another virus entirely.
Herpes.
Structure HSV-1 of shown above. This image in particular is the most detailed rendering of the virus to-date. Courtesy of UCLA.
Growing up, you always heard the disease referenced alongside common STIs like chlamydia, syphilis, and gonorrhea - amongst others. However, there’s a critical distinctinction to be made with herpes: it’s incurable.
The other thing is, though, it’s incredibly common.
The herpes disease is caused by infection with the Herpes simplex virus (HSV), which comes in two varieties known as HSV-1 and HSV-2. The remarkable thing is, 67% of the world under age 50 is infected with HSV-1, while over 11% are infected with HSV-2.
Even developed countries like the United States has HSV infection rates of approximately 50%. If you see someone with blisters around their lips, it’s probably a HSV infection flaring up.
Yet, the only symptom for the majority of people are those pesky cold sores.
HSV has been able to cause rampant, but subtle infections. The virus spreads through oral-oral contact, especially by individuals with active cold sores. After infection, HSV lies dormant within neurons, where it evades the immune system and only occasionally pops out through neuronal axons leading to the skin.
HSV itself is part of a family of viruses known as herpesviridae, which includes viruses responsible for commonplace diseases like chickenpox, shingles, or mono. The underlying characteristic of this family are lifelong, latent infections without cure. In fact, the name herpes is derived from the Greek word herpein, or to creep.
Symptoms caused by these viruses, if any, either are occasional and mild (as seen with HSV), or involve acute, isolated periods of illness (as seen with chickenpox and mono).
It’s a very successful family in terms of infection rates, but not everyone is aware of just how successful herpes is.
HSV is already known to function as an STI, causing genital herpes with certain infections. However, recent studies have begun to suggest HSV infection as having a role in the development of Alzheimer’s disease, which is a form of progressive dementia where growing plaques within the brain leads to eventual loss of function and death.
As a result, spreading awareness and educating people about just how common this infection can be is critical.
Image showing the various levels of plaque accumulation of beta amyloid within brains. Alzheimer’s patients have particularly high, progressing levels of accumulation believed to contribute to loss of function. Image courtesy of Zephyr/Science Source
The association of HSV and Alzheimer’s was first proposed around 1980, where it was largely disregarded due to controversy. However, a recent study published in 2018 establishes a definite association between HSV infections and its disruption of several neuronal pathways that contribute to Alzheimer’s disease.
As a result, what was merely a common, pesky infection might have severe implications for one’s long-term health. Alzheimer’s is similarly incredibly common, and cannot be cured or treated. Finding a way to reduce its rate of occurrence is critical, and the answer itself may lie within further studying the herpes infection.
References:
https://www.sciencedirect.com/science/article/pii/S0896627318304215?via%3Dihub
https://www.nytimes.com/2018/06/21/health/alzheimers-virus-herpes.html
http://www.who.int/news-room/fact-sheets/detail/herpes-simplex-virus