What STIs Are and How They Are Transmitted
In Regina's middle school, a teacher asks the class to write myths about HIV on the board: "you get it from a hug," "from a mosquito," "from sharing a soda." Which ones are true? Knowing how sexually transmitted infections (STIs) are transmitted helps you take care of yourself without fear and without discriminating against anyone.
What an STI is
A sexually transmitted infection (STI) is a disease caused by a microorganism (a bacterium, virus, fungus, or parasite) that passes from one person to another mainly during sexual relations. It is written STI; "STD" is used informally.
We say "infection" and not "disease" because a person can have the microorganism in the body without feeling sick. This matters later on.
Common examples:
| STI | Caused by | Type |
|---|---|---|
| Gonorrhea | bacterium | bacterial |
| Chlamydia | bacterium | bacterial |
| Syphilis | bacterium | bacterial |
| HIV | virus | viral |
| HPV (human papillomavirus) | virus | viral |
| Genital herpes | virus | viral |
Explain what a sexually transmitted infection (STI) is, mention two examples (for example, HIV and HPV), and describe two scientifically proven routes of transmission.
Explain what a sexually transmitted infection (STI) is, mention two examples (for example, HIV and HPV), and describe two scientifically proven routes of transmission.
How they are transmitted
The microorganisms that cause STIs live in body fluids (semen, vaginal secretions, blood) or in the skin and mucous membranes of the genital area. To pass from one person to another, they need an "entry point." The routes confirmed by science are three:
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Sexual contact without protection (vaginal, anal, or oral): the most common route.
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Blood: sharing needles or syringes, or using unsterilized sharp objects (for example, for piercings or tattoos done without proper hygiene), and unscreened transfusions.
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Mother to child: during pregnancy, childbirth, or breastfeeding, in some infections (HIV, syphilis).
Explain what a sexually transmitted infection (STI) is, mention two examples (for example, HIV and HPV), and describe two scientifically proven routes of transmission.
Explain what a sexually transmitted infection (STI) is, mention two examples (for example, HIV and HPV), and describe two scientifically proven routes of transmission.
What does NOT transmit an STI
HIV and other STIs are not transmitted through everyday contact. The infectious fluids do not pass through healthy skin or through the air.
| Situation | Does it transmit HIV? | Why |
|---|---|---|
| Shaking hands | No | Healthy skin is a barrier; the virus is not found in sweat. |
| Hugging or kissing on the cheek | No | There is no exchange of blood or sexual fluids. |
| Sharing utensils or cups | No | Saliva does not transmit HIV; the virus dies outside the body. |
| Using the same bathroom | No | The virus does not survive on surfaces or in water. |
| Mosquito bite | No | A mosquito does not inject blood from one person to another; the virus does not multiply in it. |
| Sex with a properly used condom | Greatly reduced risk | The condom prevents contact with fluids (studied in BARRER-CONDON). |
STIs are not transmitted through everyday contact. Indicate which of these situations do NOT transmit HIV and explain why: shaking hands, sharing cutlery, a hug, a…
STIs are not transmitted through everyday contact. Indicate which of these situations do NOT transmit HIV and explain why: shaking hands, sharing cutlery, a hug, a mosquito bite, using the same bathroom, using a condom correctly during sexual intercourse.
Cure or control: bacteria and viruses
Not all STIs are treated the same way, because the microorganisms are different.
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Bacterial STIs (gonorrhea, chlamydia, syphilis): antibiotics kill the bacteria. If treated in time, the person is cured: the infection goes away.
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Viral STIs (HIV, HPV, herpes): antibiotics do not work against viruses. There are treatments that control the infection: they keep the virus at very low levels, prevent complications, and reduce the risk of transmission, but the virus stays in the body.
"Silent" STIs
Many STIs go a long time without symptoms, or with mild symptoms that are mistaken for something else. They are called silent. Meanwhile the person can pass the infection on, and the infection can progress and cause damage (for example, infertility from untreated chlamydia or gonorrhea, or serious damage from untreated syphilis).
The solution is getting tested at a health center or clinic (IMSS, ISSSTE, Secretaría de Salud) and seeing a doctor if there are doubts. Youth-friendly health services offer confidential counseling.
Bacterial STIs (such as gonorrhea, chlamydia, or syphilis) can be cured with antibiotics if treated in time; viral STIs (such as HIV, HPV, or herpes) cannot be cured,…
Bacterial STIs (such as gonorrhea, chlamydia, or syphilis) can be cured with antibiotics if treated in time; viral STIs (such as HIV, HPV, or herpes) cannot be cured, but they can be controlled with treatment. Explain the difference between "curing" and "controlling" an infection, and why some STIs are called "silent".
How to prevent them: an overview
Knowing the routes of transmission lets us block them. The measures are developed in the following sections; here is the big picture:
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Abstinence: not having sex is the only way to completely avoid infection through sexual contact, as well as pregnancy. It is a valid choice, and each person decides when to begin their sexual life, always with consent.
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Condom: used correctly in every sexual encounter, it greatly reduces the risk of STIs and also prevents pregnancy (dual protection).
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Testing and medical care: they detect silent STIs in time. They can be done at the health center, the clinic, or youth-friendly services.
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Vaccines: there are vaccines against HPV and against hepatitis B, a viral infection that can also be transmitted sexually and through blood. They are included in the National Vaccination Schedule and are recorded in the Cartilla Nacional de Salud (National Health Card). The HPV vaccine is given during vaccination campaigns at school, at middle school ages. The vaccine prevents infection, but it does not cure someone who already has it.
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Do not share needles or unsterilized sharp objects.
Back to the beginning: on the board, the hug, the mosquito, and the shared soda are myths; the real routes are unprotected sexual contact, blood, and mother to child.