This article originally appeared on VICE US.
Herpes infects more people worldwide than any other sexually transmitted infection—and it spreads through a simple equation: One partner has the virus. Another partner doesn't. Any sexual contact between the two can infect the uninfected.
Anal, vaginal, oral, fingering—it doesn't matter; you can still share the bug. "It all depends on what's coming into contact with what," says Aaron Glatt, an infectious disease specialist and spokesperson for the Infectious Diseases Society of America.
The virus most easily enters the body through a break in the skin, Glatt says—say, an abrasion from rough sex, a cut in your mouth, or a sore from another condition. (Having any one STI increases your risk for acquiring a second.) However, herpes can also slip through the body's normal defenses, especially through mucus membranes in the mouth, eyes, genitals, or rectum.
There's no cure for herpes—and though your risk of spreading it tends to decrease over the years, it's still possible for you to infect a partner. Here's what you need to know to avoid sharing more than you bargained for.
Sex Isn't The Only Way to Test Positive
If your doc gives you a herpes diagnosis, make sure you're clear on exactly what you have, Glatt says. There are eight types of herpes simplex virus. One type, HSV-2, causes most cases of genital herpes. Another, HSV-1, most often causes cold sores—but perhaps due to all the great oral we're giving and receiving, type 1 is increasingly causing genital infections too.
If you gave every American a blood test, nine out of ten would have some evidence of infection with one of the eight types, Glatt says. But only about one in six has genital herpes.
"Ask: What type of herpes, how did I get it, and is it sexually transmitted?" Glatt says. Your doc should be able to shoot straight with you. If you test positive but the infection doesn't affect your genital area, chances are you were exposed in some other way—say, sucking on the same toy as an infected toddler way back in day care.
If you do have sores on your private parts, ask your doctor to take a swab. He or she can test the fluid from the sores for the virus, rather than just looking for antibodies the way blood tests do, Glatt says.
When those swabs come back positive, it doesn't really matter if you have type 1 or type 2, he says. You have genital herpes—most likely acquired through sexual contact with an infected person. The steps for stopping its spread are the same for both types.
You Can Pass It On Even If You're Not Having an Outbreak
Clusters of red, blistery bumps serve as the telltale sign of oral or genital herpes. When you're first infected, they usually show up within two to ten days. The sores may burst, crust over, then heal—only to come back. Recurrent outbreaks are most common during the first year, Glatt says.
The pus that oozes out of these sores contains millions of viruses, says Philip Werthman, a urologist and director of the Center for Male Reproductive Medicine in Los Angeles. "That's the most contagious time during an outbreak, when the blisters pop."
But even when your skin's clear, you're not off the hook. You might still be shedding the virus, Werthman says. Though the counts are smaller—likely in the hundreds instead of millions—herpes can still infect your partner.
In fact, about 70 percent of transmissions occur during asymptomatic periods, says James Whiteside, an obstetrician/gynecologist at the University of Cincinnati College of Medicine.
Often, this occurs soon before or after an active outbreak. Most people have a tingly, aching, itching, or stinging sensation when they're about to develop sores—a phenomenon experts call "prodrome." If you avoid sex from the moment you feel these symptoms through a couple of weeks after your sores heal, you'll reduce the risk of infecting your partner, Whiteside says.
Condoms Work—To a Point
When you're not in the midst of an active outbreak, wrap it up. Consistent condom use reduces your risk of passing along the virus by about 30 percent, according to a study in the Archives of Internal Medicine.
But of course, condoms can break and are prone to user error. Even when operated flawlessly, they're not as effective against herpes as they are against pregnancy, Glatt says. Skin-to-skin contact before the condom goes on, or between uncovered areas, still leaves the uninfected partner vulnerable.
Women Face a Greater Risk
Speaking of vulnerable—women's larger expanses of mucus membranes in and around the vagina increase their odds of catching herpes. That's especially true when they have sex with men, who are more likely than women to shed the virus even when they don't have symptoms, Whiteside says.
In fact, rates of transmission from men to women stand at about 10 percent, while women pass herpes to uninfected men only about 4 percent of the time, he says.
You Can Give It To Yourself.
Autoinoculation might sound like a scene from the new 50 Shades movie—but in fact, it's a term for the uncommon but possible circumstance of reinfecting yourself with the virus, Werthman says.
Say you have an open sore and you touch it with your hands. If you have a cut or scrape, the virus can re-enter your skin and cause painful blisters called herpetic whitlow on your fingers. If you then touch your eyes, you can also get herpetic keratitis.
You could even infect another person by touching your sores and then shaking hands, Werthman says. So, keep your hands off your junk when you have an active outbreak—or at the very least, wash or sanitize them afterward.
Antiviral Drugs Help Reduce Symptoms
If your outbreaks are frequent or severe, your doctor may prescribe medications that suppress the virus and relieve herpes symptoms. This also reduces the chances of spreading the disease. In fact, daily doses of a drug called valacyclovir cut your risk of infecting your partner by about half, according to a study in the New England Journal of Medicine.
And even more effective options may be on the horizon. In a recent JAMA study, an experimental drug called pritelivir reduced both the frequency of outbreaks and the number of days the infected person shed the virus. However, it's not yet available here in the United States.
Researchers are also working to develop a vaccine for the condition. Unlike, say, a flu shot that prevents you from catching a virus, this vaccine is given to people who already have genital herpes.
In early studies, three shots over the course of three weeks reduced the number of days in which an infected person shed virus by about half over the course of the year—potentially cutting the odds of transmission, too. However, it could be years before such methods are FDA-approved, Glatt points out. In the meantime, good old monogamy—or condoms—remain your best bet.