Chlamydia

Chlamydia, the most prevalent bacterial STI in the United States, is the result of the Chlamydia trachomatis bacterium, which can infect the urethra (bladder opening) and cervix (uterus opening). It is common in youngsters aged fifteen to nineteen. The disease is easily treated, but like other sexually transmitted infections, chlamydia tends to be silent and therefore go undiagnosed until it becomes more serious than in its early stages. Three in four women and one in two men have no symptoms. In 40 percent of cases, by the time a girl seeks medical attention, the disease has progressed to pelvic inflammatory disease (PID, described below), a major cause of female infertility and pelvic pain.
Gonorrhea

Chlamydia infection is sometimes confused with gonorrhea, another bacterial infection transmitted through vaginal and anal intercourse, and oral sex. Not only do they share many of the same symptoms, the two diseases can occur together.

Gonorrhea usually begins in the urethra (bladder opening) or the cervix. However, the rapidly proliferating Neisseria gonorrhoea bacterium can migrate to the uterus and the fallopian tubes, giving rise to pelvic inflammatory disease (PID). The infection, like chlamydia, may also involve the rectum.
Pelvic Inflammatory Disease (PID)

A number of different microorganisms can cause pelvic inflammatory disease of the upper female reproductive tract. The two most common culprits are Chlamydia trachomatis and Neisseria gonorrhea, which account for four in five cases.

Sexually active girls aged fifteen to nineteen are the most vulnerable population, partly because they are more likely than other age groups to have multiple sex partners.

PID from chlamydia infection typically produces mild symptoms or none at all, but should be treated promptly. Otherwise, like other forms of PID, it can inflame and scar the ovaries and the fallopian tubes

Because PID affects the fallopian tubes, where conception takes place, if the scarring is severe enough, the male sperm may be prevented from reaching the female egg. In other words, sterility can be the final outcome of PID
Genital Warts and Human Papillomavirus (HPV)

Scientists have identified more than one hundred types of this virus. A number of them are passed from one person to another during unprotected sex and cause benign genital warts (condylomata acuminata). Other human papillomaviruses are responsible for four in five cases of cervical cancer, in addition to several other genital malignancies.

HPV is another, often silent, STI. According to the National Institute of AIDS and Infectious Diseases, almost half the women harboring the virus exhibit no symptoms at all. Genital warts typically appear in clusters inside and outside the vagina, the cervix and/or the anus. Male venereal warts, which are far less common, form on the penis, the scrotum and/or around the anus. The pinkish or flesh-colored growths often vanish on their own.

The interventions for genital warts differ from those for other STIs. Most cases can be managed with topical treatment of the warts, though the lesions tend to return. Large warts may have to be removed using one of several surgical procedures: cryosurgery (freezing), electrocautery (burning) or laser surgery.
Syphilis

Since syphilis chancres aren’t painful and typically heal within four to six weeks, most boys don’t see a doctor. They assume the mysterious sore is gone for good, but one-third of men and women exposed to primary syphilis progress to a secondary infection. A few weeks after the chancre heals, they come down with a rash on the palms of their hands and the soles of their feet. The reddish-brown spots, about the size of a penny, can spread anywhere on the body. Other unwanted symptoms soon follow. Syphilis is still highly treatable at this point. However, a pregnant woman with primary or secondary syphilis will almost certainly transmit the bacterium to her fetus. Infection early in fetal life leads to death and abortion; infection later in pregnancy leads to a variety of problems including anemia, bleeding, swollen glands and infection of the various organs, such as the lungs, spleen and brain.