Herpes Simplex 1 vs. Herpes Simplex 2—and Why the Difference Matters

Infection with herpes simplex virus (HSV) is one of the most common infections in the world—and one of the most confusing. That’s partly because there are two types of HSV: herpes simplex virus 1 and herpes simplex virus 2, or HSV-1 and HSV-2—each of which can affect your genitals or the area around and in your mouth.

“HSV-1 and HSV-2 are two different viruses. They’re related, but they don’t morph into one another,” Anna Wald, MD, a spokesperson for the Infectious Diseases Society of America and head of the Division of Allergy and Infectious Diseases at the University of Washington, tells Health. “‘Oral’ and ‘genital’ refers to the site of the infection. Either virus can infect either site, although some are more common than others.”

Oral herpes, sometimes called cold sores or fever blisters, appears on your lips, mouth, and throat and is almost always caused by HSV-1. Most people who have oral herpes picked it up as a child, maybe from an innocent kiss or from passing toys from mouth to mouth in daycare. HSV-2 can also cause oral herpes, but it’s rare—and almost always in people who also have genital herpes.

Genital herpes (which affects the vagina, vulva, cervix, anus, penis, scrotum, butt, or inner thighs) is more often caused by HSV-2 and is transmitted primarily through genital contact. HSV-1 causes about half of all new genital herpes cases, H. Hunter Handsfield, MD, a spokesperson for the American Sexual Health Association and professor emeritus of medicine at the Center for AIDS and STD at the University of Washington, tells Health, primarily through oral sex.

What many people don’t know, though, is that herpes often has no symptoms at all. “Most HSV infections are asymptomatic,” says Dr. Wald. Most people with either infection don’t know they have it—and they most likely got it from someone who didn’t know they had it, either, she says.

If a person does experience symptoms, they can come and go. Genital herpes recurrences are more frequent with HSV-2 than with HSV-1. But the virus itself lingers. “The virus goes latent but is never totally eradicated by the immune system,” says Dr. Handsfield.

Genital herpes symptoms may include genital sores (small red bumps or white blisters), discharge, ulcers, and then scabbing. The initial outbreak is often accompanied by fever, swollen lymph nodes in your groin, a headache, and muscle aches. “It can be very painful,” says Dr. Handsfield. Oral herpes symptoms include fluid-filled sores on the lips, inside the mouth, and on the back of the throat. Lymph nodes in the neck might swell too.

Both viruses can be spread regardless of whether there are known symptoms. “That’s what’s really frustrating,” says Dr. Wald. “It’s unpredictable.”

How to know which type you have

It’s not always easy to tell. “The ideal way to know that it’s herpes and which type it is is to test at the time [lesions] are active with PCR testing,” says Dr. Handsfield. PCR, or polymerase chain reaction, testing is done on cells or fluid from herpes sores and requires “a prompt visit to the doctor because tests will remain positive only for a couple of days,” he adds.

Blood tests can be less reliable, but they may be helpful if PCR testing is negative or if a person doesn’t have an active outbreak at the time of testing, Dr. Handsfield adds.

It’s important to know which type of genital herpes you have because the risk of transmission is usually much higher with herpes simplex virus 2.

How to avoid spreading HSV-1 or HSV-2

There’s no cure and no way to 100% prevent spreading herpes. But there are effective antiviral drugs which, when taken daily, can shorten outbreaks, lower recurrences, and even reduce the risk of transmission to a partner.

There are also drug-free ways to prevent the spread of herpes, but they’re not foolproof, especially considering that many people don’t even know they have the virus.

“There is an aspect of prevention that requires cautious sexuality on everyone’s part,” says Dr. Handsfield. That means never putting areas of your body that have an active herpes outbreak (either oral or genital sores) in direct contact with other people’s mouths or genitals, he says. People with an active oral herpes outbreak shouldn’t kiss anyone or perform oral sex on a partner (unless you know that person already has the same type of herpes). Latex condoms can help prevent the spread of genital herpes, but they don’t eliminate the possibility of transmission because the sores can occur in areas that aren’t covered by a condom.

It’s also possible to spread herpes to different parts of your own body. Try not to touch any active sores, and if you do, wash your hands immediately. Don’t touch another part of your body after touching a sore or fluid from a sore without first washing your hands.

A mother can pass the herpes virus on to her newborn during delivery in what’s called “neonatal herpes.” This can be potentially devastating for the baby, possibly leading to permanent neurocognitive disabilities and other issues. “We worry about newborns acquiring HSV-1 or HSV-2 during birth,” says Dr. Wald. “The highest risk of that is if the mother has recently acquired herpes late in the pregnancy.”

Doctors will often treat pregnant women who have herpes with medication during the last month of pregnancy to prevent an active outbreak when she goes into labor, says Dr. Handsfield.

Other than stigma and discomfort if you have symptoms, infection with either HSV-1 or HSV-2 brings few long-term health problems for the average healthy adult (thankfully). However, one major exception is HIV transmission.

“On a worldwide basis, having HSV-2 is an extraordinarily potent factor for HIV transmission,” says Dr. Handsfield. People who have HSV-2 are up to six times more likely to contract HIV if they are exposed, he says. Herpes sores not only provide a way for HIV to enter the body, but even when there are no active lesions, herpes multiplies the types of cells that HIV usually targets, increasing the risk of transmission.

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