sexually transmitted infections

A number of organisms can be transmitted through sexual contact .

Some, such as Chlamydia trachomatis and Neisseria gonorrhoeae, are usually spread by sexual intercourse, while others, such as Shigella species and Entamoeba histolytica, are typically spread by other means but are also occasionally spread by sex.

Groups that are at greater risk for some sexually transmitted infections (STIs) include adolescents, men who have sex with men, and people who use illegal drugs.

While the increased risk among these groups is partially due to unsafe sexual practices, it is also due to limited access to health care. The presence of an STI in young children, unless acquired during birth, strongly suggests sexual abuse.

The initial site of infection with an STI may be the urethra, vagina, cervix, rectum, or oral pharynx. The organisms that cause these infections tend to be short-lived outside of the host, so they usually depend on direct person-to-person spread.

Most of these agents can be infectious in the absence of symptoms, so transmission often occurs from people who do not realize that they have an infection.

To reduce the spread of STIs, these infections are often reported to public health authorities so that people who have had intimate contact with the patient may be tested and treated.

Although the various pathogens that cause STIs differ in many ways, some general features should be noted.

Infection with one STI increases the risk for additional STIs. This is mainly because the risk factors are the same for all STIs. This probably explains the association between two common STIs in the United States: chlamydia and gonorrhea.

Coinfection with these two bacteria is so common that the diagnosis of either of them should lead to the treatment of both. In addition, biologic interactions between the organisms that cause STIs can increase the spread of infections.

For example, the cervicitis caused by gonorrhea or chlamydia can increase the chance that a woman who is exposed to HIV will become infected with the virus. This appears to be because the local tissue damage associated with the cervicitis allows infection with HIV.

The microbes that cause STIs can be spread from a pregnant woman to the fetus and cause severe damage to the fetus or child. Perinatally acquired C. trachomatis causes conjunctivitis, and neonatal herpes simplex virus infection is much more likely to cause visceral and CNS disease than is infection acquired later in life. Syphilis frequently causes miscarriage. HIV infection is always, eventually, fatal to children infected with the virus.

Diagnosis of STIs in pregnant women is critical because intrauterine or neonatal STI transmission can often be prevented by treatment of the mother or newborn. Bacterial infections such as gonorrhea, syphilis, and chlamydia can be easily cured with antibiotics.

Antiretroviral treatment of pregnant women with HIV infection and treatment of the newborn can reduce transmission of HIV to children from 25% to less than 2%.