Chlamydia can be transmitted during vaginal, anal, or oral sex or direct contact with infected tissue such as conjunctiva. Chlamydia can also be passed from an infected mother to her baby during vaginal childbirth.

For sexually active women who are not pregnant, screening is recommended in those under 25 and others at risk of infection. Risk factors include a history of chlamydial or other sexually transmitted infection, new or multiple sexual partners, and inconsistent condom use. For pregnant women, guidelines vary: screening women with age or other risk factors is recommended by the U.S. Preventive Services Task Force (USPSTF) (which recommends screening women under 25) and the American Academy of Family Physicians (which recommends screening women aged 25 or younger). The American College of Obstetricians and Gynecologists recommends screening all at risk, while the Centers for Disease Control and Prevention recommend universal screening of pregnant women. The USPSTF acknowledges that in some communities there may be other risk factors for infection, such as ethnicity. Evidence-based recommendations for screening initiation, intervals and termination are currently not possible. For men, the USPSTF concludes evidence is currently insufficient to determine if regular screening of men for chlamydia is beneficial. They recommend regular screening of men who are at increased risk for HIV or syphilis infection.

In the United Kingdom the National Health Service (NHS) aims to:

1. Prevent and control chlamydia infection through early detection and treatment of asymptomatic infection;

2. Reduce onward transmission to sexual partners;

3. Prevent the consequences of untreated infection;

4. Test at least 25 percent of the sexually active under 25 population annually.

5. Retest after treatment.

The infection is usually spread from one person to another through vaginal, oral, or anal sex. Men have a 20% risk of getting the infection from a single act of vaginal intercourse with an infected woman. The risk for men that have sex with men (MSM) is higher. Active MSM may get a penile infection, while passive MSM may get anorectal gonorrhea. Women have a 60–80% risk of getting the infection from a single act of vaginal intercourse with an infected man. A pregnant women can pass on the infection to her unborn infant.

A mother may transmit gonorrhea to her newborn during childbirth; when affecting the infant's eyes, it is referred to as ophthalmia neonatorum. It may be able to spread through the objects contaminated with body fluid from an infected person. The bacteria typically does not survive long outside the body, typically dying within minutes to hours.

Gonorrhea is caused by the bacterium "Neisseria gonorrhoeae". Previous infection does not confer immunity - a person who has been infected can become infected again by exposure to someone who is infected. Infected persons may be able to infect others repeatedly without having any signs or symptoms of their own.

The most common bacterial cause of NGU is "Chlamydia trachomatis", but it can also be caused by "Ureaplasma urealyticum", "Haemophilus vaginalis", "Mycoplasma genitalium", Mycoplasma hominis, Gardnerella vaginalis, Acinetobacter lwoffi, Ac.calcoclaceticus and "E.coli".

Specific age groups, persons who participate in risky sexual behavior, or those have certain health conditions may require screening. The CDC recommends that sexually active women under the age of 25 and those over 25 at risk should be screened for chlamydia and gonorrhea yearly. Appropriate times for screening are during regular pelvic examinations and preconception evaluations. Nucleic acid amplification tests are the recommended method of diagnosis for gonorrhea and chlamydia. This can be done on either urine in both men and women, vaginal or cervical swabs in women, or urethral swabs in men. Screening can be performed:

- to assess the presence of infection and prevent tubal infertility in women

- during the initial evaluation before infertility treatment

- to identify HIV infection

- for men who have sex with men

- for those who may have been exposed to hepatitis C

- for HCV

Researchers had hoped that nonoxynol-9, a vaginal microbicide would help decrease STI risk. Trials, however, have found it ineffective and it may put women at a higher risk of HIV infection.

There are many causes of NGU. This is in part due to the large variety of organisms living in the urinary tract. "Ureaplasma urealyticum" and "Mycoplasma genitalium" are some of the culprits.

NGU is also associated with Reiter's syndrome,in which triad of Arthritis,Conjunctivitis & Urethritis is there.

Prognosis is highly variable. Spontaneous remission is common. Complete cure can be obtained with proper antibiotic treatments to kill the causative bacteria, such as tetracycline, doxycycline, or erythromycin. Prognosis is more favorable with early treatment. Bacterial superinfections may complicate course. Death can occur from bowel obstruction or perforation, and follicular conjunctivitis due to autoinoculation of infectious discharge can occur.

Lymphogranuloma venereum (LGV) (also known as "Climatic bubo", "Durand–Nicolas–Favre disease", "Poradenitis inguinale", and "Strumous bubo") is a sexually transmitted disease caused by the invasive serovars L1, L2, L2a or L3 of "Chlamydia trachomatis".

LGV is primarily an infection of lymphatics and lymph nodes. "Chlamydia trachomatis" is the bacterium responsible for LGV. It gains entrance through breaks in the skin, or it can cross the epithelial cell layer of mucous membranes. The organism travels from the site of inoculation down the lymphatic channels to multiply within mononuclear phagocytes of the lymph nodes it passes.

In developed nations, it was considered rare before 2003. However, a recent outbreak in the Netherlands among gay men has led to an increase of LGV in Europe and the United States. A majority of these patients are HIV co-infected.

LGV was first described by Wallace in 1833 and again by Durand, Nicolas, and Favre in 1913. Since the 2004 Dutch outbreak many additional cases have been reported, leading to greater surveillance. Soon after the initial Dutch report, national and international health authorities launched warning initiatives and multiple LGV cases were identified in several more European countries (Belgium, France, the UK, Germany, Sweden, Italy and Switzerland) and the US and Canada. All cases reported in Amsterdam and France and a considerable percentage of LGV infections in the UK and Germany were caused by a newly discovered Chlamydia variant, L2b, a.k.a. the Amsterdam variant. The L2b variant could be traced back and was isolated from anal swabs of men who have sex with men (MSM) who visited the STI city clinic of San Francisco in 1981. This finding suggests that the recent LGV outbreak among MSM in industrialised countries is a slowly evolving epidemic. The L2b serovar has also been identified in Australia.

Regular testing for sexually transmitted infections is encouraged for prevention. The risk of contracting pelvic inflammatory disease can be reduced by the following:

- Using barrier methods such as condoms; see human sexual behavior for other listings.

- Seeking medical attention if you are experiencing symptoms of PID.

- Using hormonal combined contraceptive pills also helps in reducing the chances of PID by thickening the cervical mucosal plug & hence preventing the ascent of causative organisms from the lower genital tract.

- Seeking medical attention after learning that a current or former sex partner has, or might have had a sexually transmitted infection.

- Getting a STI history from your current partner and strongly encouraging they be tested and treated before intercourse.

- Diligence in avoiding vaginal activity, particularly intercourse, after the end of a pregnancy (delivery, miscarriage, or abortion) or certain gynecological procedures, to ensure that the cervix closes.

- Reducing the number of sexual partners.

- Sexual monogamy.

- Abstinence

PID can cause scarring inside the reproductive system, which can later cause serious complications, including chronic pelvic pain, infertility, ectopic pregnancy (the leading cause of pregnancy-related deaths in adult females), and other complications of pregnancy. Occasionally, the infection can spread to in the peritoneum causing inflammation and the formation of scar tissue on the external surface of the liver (Fitz-Hugh–Curtis syndrome).

Proctitis has many possible causes. It may occur idiopathically (idiopathic proctitis). Other causes include damage by irradiation (for example in radiation therapy for cervical cancer and prostate cancer) or as a sexually transmitted infection, as in lymphogranuloma venereum and herpes proctitis. Studies suggest a celiac disease-associated "proctitis" can result from an intolerance to gluten.

A common cause is engaging in anal sex with partner(s) infected with sexual transmitted diseases in men who have sex with men. Shared enema usage has been shown to facilitate the spread of Lymphogranuloma venereum proctitis.

Esthiomene is a medical term referring to elephantiasis of the female genitals. In the past the term has also referred to elephantiasis of the male genitalia.

Esthiomene is generally the visible result of lymphogranuloma venereum, lymphatic infection by "Chlamydia trachomatis". This sexually transmitted infection produces inflammation of the lymphatic channels in the female genitalia, followed by abscesses, fistulae, ulcerations, and fibrosis of the tissues. The tissues swell, sometimes severely, and the genitalia may grow to a massive size. Esthiomene can also be the result of tuberculosis when the infection takes hold in the genitalia, or of cancer or filariasis, infection with parasitic roundworms.

The condition is painful and sometimes disabling. People with the condition can experience mental distress from the pain and physical deformation of their genitalia. Masses can become so large they make walking difficult.

Treatment of the condition includes treatment of bacterial chlamydial infections with antibiotics such as doxycycline, or treatment of other infections present. Remaining tissue deformity can be treated with surgery such as labiaplasty to reduce the size of hypertrophied labia minora. Goals of surgery include pain relief, restoration of sexual function, and cosmetic improvement.

Anal dysplasia is most commonly linked to human papillomavirus (HPV), a usually sexually-transmitted infection. HPV is the most common sexually transmitted infection in the United States while genital herpes (HSV) was the most common sexually transmitted infection globally.

There are many different forms on prevention of syphilis and other sexually transmitted diseases in general. Prevention of syphilis includes avoiding contact of bodily fluids with an infected person. This can be particularly difficult because syphilis is usually transmitted by people who are unaware that they have the disease because they do not have any visible sores or rashes that may denote having an infection in general. Being abstinent or having mutually monogamous sex with a person who is uninfected with any type of sexually transmitted disease is the greatest guarantee of not becoming infected with syphilis or any form of a sexually transmitted disease. Using latex condoms can however reduce the risk of obtaining syphilis. In order to prevent further contamination to other individuals, benzathine penicillin is given to any contacts. Washing, douching, or urinating cannot prevent the transmission of a sexually transmitted disease in general.

Individuals obtain syphilis through a variety of circumstances. In general, syphilis can be transmitted from individual to individual through direct contact with sores that are present on the external genitals, vagina, rectum, anus, lips, or mouth. Transmission can occur through any form of sexual contact, including vaginal, anal, and oral sex. In addition, women who are pregnant and infected with syphilis can transmit the disease onto their child as well. If transmission has occurred, it is important to check up immediately with a physician to avoid further damage.

Anal warts are irregular, verrucous lesions caused by human papilloma virus. Anal warts are usually transmitted by unprotected, anoreceptive intercourse. Anal warts may be asymptomatic, or may cause rectal discharge, anal wetness, rectal bleeding, and pruritus ani. Lesions can also occur within the anal canal, where they are more likely to create symptoms.

Proctitis is an inflammation of the anus and the lining of the rectum, affecting only the last 6 inches of the rectum.

Rectovaginal fistulas are often the result of trauma during childbirth (in which case it is known as obstetric fistula) where improper medical interventions are used, such as episiotomy with forceps/vacuum extraction or in situations where there is inadequate health care, such as in some developing countries. Rectovaginal fistula is said to be known as the leading cause in maternal death in developing countries. Risk factors include prolonged labour, difficult instrumental delivery and paramedian episiotomy. Rates in Eritrea are estimated as high as 350 per 100,000 vaginal births. Fistulas can also develop as a result of physical trauma to either the vagina or anus, including from rape. Women with rectovaginal fistulae are often stigmatized in developing countries, and become outcasts.

Rectovaginal fistula can also be a symptom of various diseases, including infection by lymphogranuloma venereum, or the unintended result of surgery, such as episiotomy or sexual reassignment surgery. They may present as a complication of vaginal surgery, including vaginal hysterectomy. They are a recognized presentation of rectal carcinoma or rarely diverticular disease of the bowel or Crohn's disease. They are seen rarely after radiotherapy treatment for cervical cancer.

Proctitis is inflammation of the anal canal and the distal of the rectum.

Proctitis has many causes, such as infections or intercourse.

Tuberculosis proctitis can create a mucous discharge.

Vaginal gas that involves strong odor or fecal matter may be a result of colovaginal fistula, a serious condition involving a tear between the vagina and colon, which can result from surgery, child birth, diseases (such as Crohn's disease), and other causes. This condition can lead to urinary tract infection and other complications. Vaginal gas can also be a symptom of an internal female genital prolapse, a condition most often caused by childbirth.

Puffs or small amounts of air passed into the vaginal cavity during cunnilingus will not cause any known issues, however "forcing" or purposely blowing air at force into the vaginal cavity can cause an air embolism, which in very rare cases can be potentially dangerous for the woman, and if pregnant, for the fetus.

Bacterial, viral, and protozoal infections may occur in the area surround the rectum. These may be the result of a sexually transmitted disease.

A chancre ( ) is a painless ulceration (sore) most commonly formed during the primary stage of syphilis. This infectious lesion forms approximately 21 days after the initial exposure to "Treponema pallidum", the gram-negative spirochaete bacterium yielding syphilis. Chancres transmit the sexually transmissible disease of syphilis through direct physical contact. These ulcers usually form on or around the anus, mouth, penis, and vagina. Chancres may diminish between four and eight weeks without the application of medication.

Chancres, as well as being painless ulcerations formed during the primary stage of syphilis, are associated with the African trypanosomiasis sleeping sickness, surrounding the area of the tsetse fly bite.

An anorectal abscess is an infection that forms a pocket of pus within the tissues around the anus. It is treated surgically by incision and drainage.

The Jarisch-Herxheimer reaction, which is the response to the body after endotoxins are released by the death of harmful organisms in the human body, starts usually during the first day of antibiotic treatment. The reaction increases the person's body temperature, decreases the overall blood pressure (both systolic and diastolic levels), and results in leukopenia and rigors in the body. This reaction can occur during any treatment of spirochete diseases.

It is important to realize that syphilis can recur. An individual who has had the disease once, even if it has been treated, does not prevent the person from experiencing recurrence of syphilis. Individuals can be re-infected, and because syphilis sores can be hidden, it may not be obvious that the individual is infected with syphilis. In these cases, it is vital to become tested and treated immediately to reduce spread of the infection.