Herpes simplex virus type 1
Understanding HSV-1 — the common virus with a serious side
HSV-1 infects most of the world's population and is usually mild. But it can, in rare cases, cause severe and even life-threatening illness. This guide explains both truths clearly, so you can take the real risks seriously without the myths.
HSV-1 at a glance
The big picture, in the numbers most people never hear.
People under 50 estimated to carry HSV-1 worldwide — about 64% of that age group (WHO, 2020).
Once acquired, the virus stays in the body permanently. There is currently no cure and no vaccine.
Many people never notice symptoms, and the virus can spread even when no sores are visible.
In uncommon cases it causes brain, eye or newborn infections that can threaten sight or life.
So how dangerous is HSV-1, really?
Both things are true at once, and honest information has to hold both. For the large majority of people, HSV-1 is a mild, manageable condition — most often the cold sores (fever blisters) that appear around the lips and clear up on their own. Many carriers never have a single noticeable symptom.
But "usually mild" is not the same as "harmless." In a small number of cases, HSV-1 causes complications that are genuinely dangerous: inflammation of the brain, infection of the eye that can lead to blindness, and severe illness in newborns and in people whose immune systems are weakened. These outcomes are rare — but serious, and sometimes fatal. They are also the reason the virus deserves respect rather than either panic or dismissal.
This site aims to give you the full picture: the everyday reality most people experience, and the warning signs that are true emergencies.
Seek emergency care right away if HSV appears with any of these
Confusion, a severe or unusual headache, a stiff neck, seizures, or fever with altered behaviour (possible brain infection); a painful red eye or sudden change in vision; or any herpes sore in a newborn baby. These can be medical emergencies. Call your local emergency number or go to an emergency department.
Explore the facts
Straightforward, sourced answers to the questions that matter most.
Signs & symptoms
What HSV-1 looks like — from cold sores to first-time infections — and what's easy to miss.
Read more →How it spreads
Saliva, skin contact, and "silent" transmission with no visible sore.
Read more →Serious risks
The rare-but-severe complications: brain, eye, newborn, and immunocompromised infection.
Read more →Prevention & treatment
How to lower the risk of spreading it, and what antiviral treatment can and can't do.
Read more →Myths & facts
Untangling stigma and misinformation from what the evidence actually shows.
Read more →Sources
The health authorities and medical references this guide is built on.
Read more →