biology

Sexually transmitted infection

Sexually transmitted infection is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sexually transmitted infection rather than just read about it. In short: A sexually transmitted infection (STI), also known as a sexually transmitted disease (STD) or venereal disease (VD), is an infection that is spread by sexual activity, especially vaginal intercourse, anal sex, oral sex, or sometimes manual sex. STIs often do not initially cause symptoms, which results in a risk of transmitting them to others.

Key takeaways

Sexually transmitted infection belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sexually transmitted infection to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sexually transmitted infection from memory before moving on to harder problems.

Reference excerpt

A sexually transmitted infection (STI), also known as a sexually transmitted disease (STD) or venereal disease (VD), is an infection that is spread by sexual activity, especially vaginal intercourse, anal sex, oral sex, or sometimes manual sex. STIs often do not initially cause symptoms, which results in a risk of transmitting them to others. The term sexually transmitted infection is generally preferred over sexually transmitted disease or venereal disease, as it includes cases with no symptomatic disease. Symptoms and signs of STIs may include vaginal discharge, penile discharge, ulcers on or around the genitals, and pelvic pain. Some STIs can cause infertility. Bacterial STIs include chlamydia, gonorrhea, and syphilis. Viral STIs include genital warts, genital herpes, and HIV/AIDS. Parasitic STIs include trichomoniasis. Most STIs, such as syphilis, gonorrhea, chlamydia and trichomoniasis, are treatable and curable. Others, such as HIV/AIDS and genital herpes, are not curable. Some vaccinations have been known to decrease the risk of certain infections including hepatitis B and a few types of HPV. Using condoms, having a smaller number of sexual partners, and being in a relationship in which each person only has sex with the other are all safe sex practises that decreases the risk of contracting STIs. Comprehensive sex education may also be useful. STI diagnostic tests are usually easily available in the developed world, but they are often unavailable in the developing world. There is often shame and stigma associated with STIs. In 2015, STIs (excluding HIV) resulted in 108,000 deaths worldwide. Globally, in 2015, about 1.1 billion people had STIs other than HIV/AIDS. About 500 million have syphilis, gonorrhea, chlamydia or trichomoniasis. At least an additional 530 million have genital herpes, and 290 million women have human papillomavirus. Historical documentation of STIs in antiquity dates back to at least the Ebers Papyrus (c. 1550 BCE) and the Hebrew Bible/Old Testament (8th/7th C. BCE).

Signs and symptoms

Not all STIs are symptomatic, and symptoms may not appear immediately after infection. In some instances a disease can be carried with no symptoms, which leaves a greater risk of passing it on to others. Depending on the disease, some untreated STIs can lead to infertility, chronic pain or death. The presence of an STI in prepubescent children may indicate sexual abuse.

Cause

Transmission A sexually transmitted infection present in a pregnant woman may be passed on to the infant before or after birth.

Bacterial Chancroid (Haemophilus ducreyi) Chlamydia (Chlamydia trachomatis) Gonorrhea (Neisseria gonorrhoeae) Granuloma inguinale or (Klebsiella granulomatis) Mycoplasma genitalium Mycoplasma hominis Syphilis (Treponema pallidum) Ureaplasma infection

Viral

Viral hepatitis (hepatitis B virus)—saliva, venereal fluids.(Note: hepatitis A and hepatitis E are transmitted via the fecal–oral route; hepatitis C is rarely sexually transmittable, and the route of transmission of hepatitis D (only if infected with B) is uncertain, but may include sexual transmission.) Herpes simplex (Herpes simplex virus 1, 2) skin and mucosal, transmissible with or without visible blisters HIV (Human Immunodeficiency Virus)—venereal fluids, semen, breast milk, blood HPV (Human Papillomavirus)—skin and mucosal contact. 'High risk' types of HPV cause almost all cervical cancers, as well as some anal, penile, and vulvar cancer. Some other types of HPV cause genital warts. Molluscum contagiosum (molluscum contagiosum virus MCV)—close contact Zika virus

Parasites Crab louse, colloquially known as "crabs" or "pubic lice" (Pthirus pubis). The infestation and accompanying inflammation is Pediculosis pubis Scabies (Sarcoptes scabiei) Trichomoniasis (Trichomonas vaginalis), colloquially known as "trich"

Fungal Trichophyton mentagrophytes type VII is an emerging fungal infection (tinea or ringworm) that is spread through sexual activity and other close contact.

Main types Sexually transmitted infections include:

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Sexually transmitted infection

Start with the simplest possible case. Write down what Sexually transmitted infection claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sexually transmitted infection before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sexually transmitted infection ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sexually transmitted infection

In research: Sexually transmitted infection appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sexually transmitted infection in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sexually transmitted infection is common in secondary-school and first-year university syllabi. It links to neighbouring topics Disease transmission, Mycoplasma, Sexually transmitted infections, so understanding it makes those chapters shorter.
In everyday life: Look for Sexually transmitted infection outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Sexually transmitted infection” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Sexually transmitted infection in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sexually transmitted infection means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sexually transmitted infection out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sexually transmitted infection in simple terms?

Why does Sexually transmitted infection matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sexually transmitted infection?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sexually transmitted infection.