Herpes Simplex Virus 1 vs. Herpes Simplex Virus 2—Understanding the Difference

For starters, herpes simplex virus 2 is much more likely to be spread through sexual contact.

Herpes simplex virus (HSV) is one of the most common infections—and one of the most confusing. That's because there are two types: herpes simplex virus 1 (HSV-1) and herpes simplex virus 2 (HSV-2). Both can affect your genitals or the area around and in your mouth.

HSV-1 vs. HSV-2

HSV-1 most commonly causes oral herpes, sometimes called cold sores or fever blisters, on your lips, mouth, and throat. The Centers for Disease Control and Prevention (CDC) explained that most people with oral herpes picked it up as a child, maybe from a kiss or from passing toys from mouth to mouth in daycare.

HSV-2 can also cause oral herpes, but it's less common. HSV-2 is transmitted primarily through genital contact. It is the leading cause of genital herpes, a sexually transmitted infection (STI) that can occur on the vagina, vulva, cervix, anus, penis, scrotum, butt, or inner thighs, according to the World Health Organization (WHO).

"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, told Health. "'Oral' and 'genital' refer to the site of the infection. Either virus can infect either site."

While HSV-2 primarily causes genital infections, HSV-1 can cause them, too, primarily through oral sex. 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, told Health.

Symptoms of HSV-2 vs. HSV-1

What many people don't know is that herpes often has no symptoms at all. Most people with either infection don't know that they have it or that they likely got it from someone who didn't know they had it, either, said Dr. Wald.

If a person does experience symptoms, they tend to come and go. The CDC notes that 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," said Dr. Handsfield. Also, according to the CDC, it is estimated that in individuals between the ages of 14 to 49 years old infected with HSV-2, 87.4% don't know they have it.

The CDC explains that genital herpes symptoms may include genital sores (small red bumps or white blisters), discharge, ulcers, and 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," said 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 spread regardless of whether there are known symptoms. "That's what's really frustrating," said Dr. Wald. "It's unpredictable."

How to Know Which Type You Have

It's not always easy to tell if someone has HSV-1 or HSV-2. "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," said Dr. Handsfield. Johns Hopkins Medicine explained that PCR or polymerase chain reaction testing is done on cells or fluid from an active herpes infection, meaning herpes sores or lesions are present.

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, said Dr. Handsfield.

It's important to know which type of genital herpes you have so you can take steps towards prevention and treatment.

How to Avoid Spreading HSV-1 or HSV-2

While there's no cure or way to prevent spreading herpes entirely, the CDC described treatment options to reduce symptoms, outbreaks, and other precautions to minimize spread. One type of medication, called antiviral drugs, can shorten outbreaks, lower recurrences, and even reduce the risk of transmission to a partner when they are taken as prescribed.

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," said 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. For example, 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). In addition, latex condoms can help prevent the spread of genital herpes. Still, 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; if you do, wash your hands immediately. Likewise, don't touch another part of your body after touching a sore or fluid from a sore without first washing your hands.

Neonatal HSV Infections

A pregnant individual can pass the herpes virus on to their newborn during delivery in what's called "neonatal herpes," according to Boston Children's Hospital. 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," said Dr. Wald. "The highest risk of that is if the mother has...acquired herpes late in the pregnancy."

Doctors will often treat pregnant individuals who have genital herpes with medication during the last month of pregnancy to prevent an active outbreak when they go into labor, said Dr. Handsfield.

Living With an HSV-1 or HSV-2 Infection

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. However, one major exception is HIV transmission.

"On a worldwide basis, having HSV-2 is an extraordinarily potent factor for HIV transmission," said Dr. Handsfield. People who have HSV-2 are up to six times more likely to contract HIV if they are exposed. 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.

So, if you notice symptoms of HSV-1 or HSV-2, or have concerns due to past or current partners, talk with your healthcare provider to determine your risk factors, establish a diagnosis, and discuss treatment options, if necessary.

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