Yes, herpes is a virus. Specifically, herpes simplex virus (HSV) is a double-stranded DNA virus that infects human cells, establishes a permanent presence in the nervous system, and can reactivate throughout a person’s life. There are two types: HSV-1, which most commonly causes oral cold sores, and HSV-2, which typically causes genital herpes. Both are extraordinarily common, with an estimated 3.8 billion people under age 50 carrying HSV-1 and about 520 million people aged 15 to 49 carrying HSV-2 worldwide.
What Type of Virus Herpes Is
Herpes simplex virus belongs to a large family of viruses called Orthoherpesviridae. This family includes not just the two herpes simplex types but also the viruses behind chickenpox, shingles, and mononucleosis. HSV-1 and HSV-2 are both classified under the subfamily Alphaherpesvirinae and the genus Simplexvirus, which means they share a similar structure and behavior but differ enough to be considered separate species.
Unlike bacteria, which are living organisms that can reproduce on their own, viruses like HSV are essentially packages of genetic material wrapped in protein. They cannot replicate without hijacking a host cell’s machinery. This distinction matters because it explains why antibiotics don’t work against herpes. Antiviral medications are needed instead, and they work by a completely different mechanism.
How the Virus Enters and Takes Over Cells
HSV has a layered structure: a core of linear DNA roughly 152,000 base pairs long, surrounded by a protein shell called a capsid, a layer of proteins called the tegument, and an outer envelope studded with proteins that help it latch onto human cells. Those surface proteins bind to receptors on your cells and fuse with the cell membrane, releasing the capsid into the cell’s interior.
Once inside, the capsid rides along the cell’s internal transport system (using a motor protein called dynein) to reach the nucleus. The capsid docks at a pore in the nuclear membrane, and the viral DNA is injected through that pore, much like a syringe. The empty capsid stays outside the nucleus while the DNA enters and begins commandeering the cell’s machinery to produce new copies of itself. These new virus particles then assemble, exit the cell, and go on to infect neighboring cells.
Why Herpes Never Leaves Your Body
The defining feature of herpes is latency. After the initial infection, the virus travels along nerve fibers and settles into clusters of nerve cells called sensory ganglia. HSV-1 typically lodges in the trigeminal ganglion near the jaw, while HSV-2 usually takes up residence in ganglia near the base of the spine. Once there, the virus essentially goes quiet. It stops replicating and produces only a small transcript that helps it stay hidden from the immune system.
Your immune system plays an active role in keeping the virus dormant. Specialized immune cells stationed near the infected nerve cells continuously suppress reactivation. When the balance shifts, whether from stress, illness, immune suppression, or other triggers, the virus can reactivate, travel back down the nerve fibers to the skin, and cause a new outbreak. This cycle of dormancy and reactivation lasts for life.
How Herpes Spreads
HSV spreads through direct contact with infected skin or mucous membranes. For HSV-1, this often means kissing or sharing utensils during an active cold sore. For HSV-2, transmission occurs primarily through sexual contact during periods of genital shedding.
What makes herpes particularly easy to spread is that the virus can be present on the skin without any visible symptoms. People with HSV-2 shed the virus from genital skin about 18% of the time, and roughly 80% of that shedding happens without any noticeable sores or symptoms. This means most transmissions occur when the infected person has no idea they’re contagious.
How It’s Diagnosed
The most reliable way to test for herpes is a swab taken directly from an active blister or sore. These swab-based tests, which detect viral DNA, work best when the sore is fresh and hasn’t started crusting over.
Blood tests are available for people without active sores, but they have significant limitations. These tests look for antibodies your body produces in response to infection, not the virus itself. After exposure, it can take up to 16 weeks for antibody levels to become detectable, so testing too early can produce a false negative. False positives are also more common with herpes blood tests than with tests for other sexually transmitted infections like chlamydia or gonorrhea. A positive blood test in someone with low risk of infection is particularly unreliable, which is one reason routine screening isn’t recommended for everyone.
How Antiviral Treatment Works
Because herpes is a virus, not a bacterium, treatment relies on antiviral medications rather than antibiotics. The most commonly prescribed options, acyclovir and valacyclovir, work by mimicking one of the building blocks of DNA. When the virus tries to use these drugs to copy its genetic material, the process stalls. The result is that viral replication slows dramatically, which shortens outbreaks and reduces their severity.
These medications don’t eliminate the virus from the body. The latent copies hiding in nerve cells are not actively replicating, so antivirals can’t reach them. What the drugs can do is reduce the frequency of outbreaks when taken daily (called suppressive therapy) and lower the risk of transmitting the virus to a partner. For many people, outbreaks become less frequent over time even without daily medication, as the immune system gets better at controlling reactivation.
No Vaccine Yet, but Research Continues
There is currently no approved vaccine for either type of herpes simplex virus. Developing one has proven difficult, partly because the virus’s ability to hide in nerve cells makes it a challenging target for the immune system. Several candidates are in various stages of testing. Moderna completed a Phase 1/2 trial of an mRNA-based therapeutic vaccine candidate for HSV-2 in early 2025, designed to reduce outbreaks in people already infected. Results from that and other trials will determine whether any candidate moves forward to larger studies.