Herpes simplex virus infects skin or mucous membrane cells, then hides permanently in your nerve cells, cycling between dormant periods and active outbreaks that produce painful blisters. Over 846 million people between the ages of 15 and 49 are living with genital herpes worldwide, making it one of the most common viral infections on the planet. There are two types: HSV-1, which typically causes oral cold sores, and HSV-2, which primarily causes genital outbreaks, though either type can infect either location.
How the Virus Gets Into Your Cells
Herpes needs direct contact with skin or mucous membranes to spread. Once the virus touches a susceptible surface, it latches onto sugar-coated molecules on the outside of your cells. This initial grip is loose, like a hand reaching for a railing. The virus then locks onto more specific receptors that pull it close enough to fuse its outer envelope with your cell membrane, slipping its genetic material inside.
Once inside, the virus hijacks the cell’s own transport system to shuttle its DNA into the nucleus, where your cell’s own machinery starts copying viral genes and assembling new virus particles. In skin cells and other non-nerve cells, this process happens fast. The cell fills with new copies of the virus, eventually rupturing and releasing them to infect neighboring cells. That wave of cell destruction is what creates the blisters and sores you see on the surface.
Why It Never Leaves Your Body
What makes herpes different from many other infections is what it does after that initial burst of activity. Some virus particles travel along nerve fibers and settle into clusters of nerve cells called ganglia. HSV-1 typically parks itself in the trigeminal ganglia near the base of the skull, which serve the face and mouth. HSV-2 favors the sacral ganglia at the base of the spine, which connect to the genital area.
Inside these neurons, the virus goes quiet. It stops replicating and tucks its DNA into the cell’s nucleus, entering a state called latency. Your immune system can’t find it there because the nerve cell stops displaying the viral proteins that would normally flag it for destruction. The virus produces only a small set of molecules during latency, just enough to maintain its foothold without triggering an alarm. This is why herpes is a lifelong infection. Your body’s defenses can control it but never fully eliminate it.
How Your Immune System Fights Back
Your body does mount a significant response. Specialized immune cells called CD8+ T cells are the primary enforcers. They park themselves around the nerve clusters where the virus hides and produce signaling molecules that suppress viral reactivation. These T cells remain at their posts for years, constantly on guard, which suggests the virus periodically tries to wake up even when you don’t notice any symptoms.
Antibodies play a surprisingly minor role. Animal studies show that transferring antibodies from an immune animal to a non-immune one doesn’t meaningfully reduce viral replication in either the genital tract or the nervous system. Antibodies can help prevent a new infection from taking hold, but once the virus is established, T cells do the heavy lifting.
The virus fights back with its own arsenal. It produces proteins that prevent infected cells from displaying distress signals on their surface, hiding them from immune detection. Other viral proteins block the production of interferons, the chemical alarms your cells normally release when invaded. This molecular arms race between virus and immune system is what keeps herpes in a permanent stalemate rather than resolving the infection.
What an Outbreak Looks and Feels Like
When the virus reactivates, it travels back down the nerve fibers to the skin’s surface. Many people first notice a prodrome: burning, itching, or tingling at the site where the virus originally entered the body. Some feel aching in the lower back, buttocks, thighs, or knees. This warning phase happens because the virus is actively traveling through nerve pathways before reaching the skin.
Within a day or two, small fluid-filled blisters appear. These can show up on the genitals, buttocks, mouth, or surrounding areas depending on the type of infection. The blisters break open, forming shallow ulcers that weep fluid loaded with active virus. Over several days, the sores crust over and heal.
The first outbreak is almost always the worst, lasting two to four weeks. Recurrent outbreaks heal faster, typically within three to seven days, and tend to be less painful. Over time, most people experience fewer and less severe episodes as the immune system gets better at containing reactivation.
Spreading Without Symptoms
One of the most consequential things herpes does is shed virus even when no sores are visible. People with genital HSV-2 shed the virus on roughly 18% of days, and about 80% of that shedding happens without any noticeable symptoms. This is why most new herpes infections are transmitted by someone who doesn’t know they’re contagious at that moment. Studies using daily swabs found that 30% of transmission events occurred when no lesion wider than 1 millimeter was present.
This invisible shedding also explains why herpes spreads so effectively through populations. Many carriers have never had a recognized outbreak and don’t realize they carry the virus.
Serious Complications
For most people, herpes is an uncomfortable but manageable condition. In certain situations, though, it can cause significant harm.
Herpes is the most common cause of corneal blindness in developed countries. The virus can infect nearly every structure in the eye, from the eyelids to the retina. Corneal infections create branching, tree-like ulcers on the eye’s surface. Deeper infections trigger chronic inflammation that can thin and scar the cornea. Retinal infections, called acute retinal necrosis, cause vision loss, floaters, and pain. About one-third of people with retinal herpes in one eye eventually develop it in the other.
Herpes encephalitis, an infection of the brain, is rare but life-threatening. It can develop when the virus travels along nerve pathways into brain tissue, causing inflammation that damages neurons. People with certain skin conditions like eczema are at elevated risk because widespread skin outbreaks can give the virus more opportunities to reach the central nervous system.
Risk to Newborns
Neonatal herpes is one of the most dangerous complications. A mother who acquires a new genital herpes infection near the time of delivery has a 25% to 60% chance of transmitting it to the baby during vaginal birth. The risk drops dramatically for mothers with an established infection: below 2%. The difference comes down to antibodies. A mother with a longstanding infection has built up antibodies that cross the placenta and offer the baby some protection. A brand-new infection hasn’t had time to generate that shield.
How Treatment Works
Antiviral medications can’t cure herpes, but they significantly reduce its impact. Daily suppressive therapy cuts the frequency of outbreaks by 70% to 80% in people with frequent recurrences. It also lowers the rate of transmission to uninfected sexual partners, though it doesn’t eliminate the risk entirely.
For individual outbreaks, starting antiviral treatment during the prodrome or within the first day of sores appearing shortens healing time and reduces severity. The medications work by blocking the enzyme the virus uses to copy its DNA, slowing replication enough for the immune system to regain control.
How Effectively Condoms Protect
Condoms provide meaningful but imperfect protection. One study of couples where one partner had HSV-2 found condoms were 96% effective at preventing transmission from men to women, but only 65% effective from women to men. The difference likely reflects anatomy: male-to-female transmission involves virus deposited in an area largely covered by the condom, while female-to-male transmission can involve viral shedding from skin the condom doesn’t cover. Combining condom use with daily antiviral therapy offers the strongest reduction in transmission risk available without abstinence.