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From Hep A to Zika: 9 infections you didn't know were STIs

Not to freak you out, but there are a bunch of bacteria, viruses, and parasites that can be transmitted through sex.

by Ina Park, MD, MS

You probably know the most common sexually transmitted infections (STIs, a.k.a. STDs), like chlamydia, gonorrhea, syphilis, trichomoniasis, HPV, HIV, and herpes. But did you know that there are dozens of less-well-known bacteria, viruses, and parasites that can be sexually transmitted? Here are nine more infections you should know about, from A to Zika.


Hepatitis A is often associated with oral-anal contact (a.k.a. rimming), but it can actually be transmitted through any kind of sexual activity. Vaccination is the best way to prevent the spread of hepatitis A. All men who have sex with men should be vaccinated, as well as sexually active adults who inject drugs, have chronic liver disease, or have sex partners who are infected with hepatitis A.

Hepatitis B is easily transmitted through sexual activity and is actually 50-100 times more infectious than HIV. Vaccination is recommended for all children and adolescents and for any sexually active adult who has multiple partners, plus a long list of others who may be at risk.

Hepatitis C is not easily transmitted through sex, but transmission can happen. Having another STI or HIV at the same time, having multiple partners, or practicing certain types of sex (e.g. fisting) can increase the risk of getting hepatitis C through sex. Since there isn’t a vaccine, the best way to avoid hepatitis C is to have safer sex and avoid sharing needles and other equipment if you use injection drugs.

Should you worry? If you’re diagnosed with hepatitis, you may have no symptoms or may have fatigue, nausea, and yellowing of the skin/eyes. People with hepatitis A usually get better on their own—they may be ill for weeks to several months, but the infection does not become chronic. Some people with hepatitis B or hepatitis C end up with chronic infections that cause long-term liver problems, so all people who are chronically infected need ongoing monitoring by a health care provider.

M & Ms

Meningococcal disease can be spread through exchange of saliva, which can happen through sex, kissing, or even just from living in close quarters with another person. Vaccination is recommended for all 11-12-year-olds, college freshmen living in dormitories, and other adults who are at risk. Outbreaks have occurred among gay and bisexual men in Chicago, New York, Los Angeles, and in the state of Minnesota, so in these areas, men who have sex with men should also be vaccinated.

Should you worry? Meningococcal disease can cause severe illness, including death. If you have symptoms of meningococcal disease including fever, headache, a stiff neck or a rash, you should seek medical attention as soon as possible.

Mycoplasma genitalium (“M. gen”) is a tiny bacterium that can reside in the genitals, anus, and throat. If you become infected, you may have no symptoms, you may develop discharge from the penis or the vagina, or men may have pain when they pee. Since many health care providers don’t have access to a test for M. gen, they’ll need to treat you based on your symptoms. The most common treatment for chlamydia may also treat M. gen, but if you still have discharge or pain after treatment, your provider may need to give you additional antibiotics.

Should you worry? It may take multiple rounds of antibiotics but M. gen is completely curable. Once you’re cured, you are able to get it again, just like with gonorrhea or chlamydia.

Molluscum contagiosum is a virus that causes white, pink, or flesh-colored bumps on the skin with a characteristic dimple in the center. They can appear anywhere on the body, including on the genitals or anus. Molluscum contagiosum is actually most common among kids (ages 1 to 10) but it’s transmitted among adults in a wide variety of situations involving skin-to-skin contact or contact with an infected surface. While sex is one of the activities that can cause transmission, molluscum contagiosum can also be spread through sharing towels or clothing, exercising on a mat used by others (e.g. wrestlers, gymnasts), or sharing toys (e.g. kids sharing toy trucks, or adults sharing sex toys). Preventing the spread of molluscum contagiosum involves old-fashioned hand washing, keeping lesions covered with watertight bandages, and not sharing towels or sports gear. Don’t pick, scratch, or shave in an area with lesions—they’ll just get worse.

Should you worry? Molluscum contagiosum usually doesn’t have any effects other than the bumps that it causes, and it typically goes away on its own without treatment in 6-12 months. If you have bumps or mollusca in the genital or anal area, it’s a good idea to see your health care provider to get checked for other STIs.

P & S

Pubic lice, or “crabs,” have three forms: the egg (a.k.a. nit), the nymph, and the adult. The adult louse is the one that resembles the miniature crab, with two large front legs and pincer claws. Lice need your blood to survive, so if they end up falling off your body, they’ll die within 1-2 days. Pubic lice is only spread person-to-person, so if someone claims they caught it from their pet, don’t believe them. Pubic lice are becoming less common because widespread bikini waxing and other hair removal practices have destroyed their habitat, making them an endangered species. (I don’t think many of us will shed a tear if they become extinct.)

Should you worry? Luckily, there are multiple treatments for pubic lice, including things you can buy online or at a drug store without a prescription, such as 1% permethrin.

Scabies is an infestation of the skin caused by a mite that burrows into the upper layer of the skin, makes itself at home, and starts laying eggs. Your skin does not take kindly to these invaders and will begin to break out in an intensely itchy rash, with symptoms that often worsen at night. The rash looks almost like acne but most commonly spares the face, instead occurring on other parts of the body: web space between fingers, at the folds of the wrist, elbow or knee, armpits, genitals, buttocks and between the shoulder blades. Any direct skin-to-skin contact with someone who has scabies (sexual contact or even just cuddling) can result in transmission. Scabies outbreaks are most common in group residence situations such as shelters, nursing homes, college dorms, and correctional facilities.

Should you worry? If you think you have scabies, go see your health care provider because the medications that cure scabies are available by prescription only. They work well, but recovering from scabies requires patience since the itching can last for several weeks after successful treatment.

Last but not least: Zika

Zika virus has mainly been sexually transmitted from men to women, but there are also a few known cases of transmission from women to men and men to men. The CDC warns that Zika can be transmitted via multiple types of sexFor men living in a Zika-affected area, consider abstaining or using condoms for as long as is Zika around. including vaginal, anal, and oral sex, and sharing of sex toys—meaning anyone who has sex with a Zika-infected partner could potentially become infected.

For men visiting a Zika-affected area, either abstain from sex or use a method that prevents STIs such as condoms for at least 6 months after leaving that area, even if you don’t have any symptoms of the virus. If you’ve been diagnosed with the virus or had symptoms of Zika, same deal—abstain from sex or use condoms for at least 6 months.

If you are a woman trying to conceive, its best to wait at least 8 weeks after leaving a Zika-affected area before you try to get pregnant. Women with symptoms of Zika should also wait to conceive for at least 8 weeks after symptoms first appeared. If you’re not trying to get pregnant right now, or if you need to wait those 8 weeks, make sure your birth control is covered.

Ready to have a baby and live in an area with Zika, or think you or your partner may have been exposed to the virus? Talk to a health care provider about what precautions to take before trying for a pregnancy.

Should you worry? Although most people with Zika will improve on their own, Zika has been linked to a rare illness affecting the nervous system. Infection during pregnancy has also been linked to severe birth defects such as microcephaly. Our understanding of Zika is changing quickly, so consult the CDC website for the latest updates.

Now what?

While some of the infections you’ve just read about won’t be totally preventable with condoms, for hepatitis C, Mycoplasma genitalium, and Zika, using condoms will help prevent sexual transmission. For hepatitis B, using condoms and getting vaccinated are your best bets. Information is power, so take sensible precautions, then get out there and have fun!

Ina Park, MD, MS has dressed up as a giant condom more than once to encourage awareness of STIs and safer sex. She’s currently the Medical Director for the California STD/HIV Prevention Training Center and an Associate Professor at the University of California San Francisco-School of Medicine. She’s also raising two rambunctious sons whom she refers to as the “future STI transmitters of America.” When she’s not at work or with her family, she’s practicing yoga and eating as much as she can.

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