HIV is a virus that destroys the
body’s ability to fight infection. People who have HIV may not look or feel sick for
a long time after infection. If you are not diagnosed early and treated, you are
at
high risk of developing many life-threatening diseases and certain forms of cancer.
The virus is passed on most often during sexual activity. It can also be passed on
by
sharing needles used to inject drugs. HIV can be passed to your baby during
pregnancy, and labor and delivery, and through breastfeeding. If you know before
becoming pregnant or early in your pregnancy that you are HIV-positive, you can get
treatment that greatly lowers your chance of passing on the virus to your child. 

HPV is one of the most common
STIs. Some types of HPV can cause genital warts. These can happen on the inside or
outside areas of the genitals. They may spread to the surrounding skin or to a sexual
partner. Many other types of HPV cause no symptoms, so you may not know that you are
infected. In most cases, the virus goes away and doesn’t cause more health problems.
But if the virus lasts, normal cells can change and become abnormal. Women with an
HPV infection with high-risk types such as HPV 16 and 18 have an increased risk of
getting cervical cancer. Pap tests can detect HPV infection, as well as abnormal
cervical cells. An HPV vaccine protects against the types of HPV that cause most
cervical cancers. It also protects against most genital warts in both men and women,
and against anal cancer in men. Even with treatment for genital warts, the virus
remains in the body and warts can reappear. Certain types of HPV can also cause warts
on other body parts such as the hands. These are called common warts. These don’t
generally cause health problems. If a pregnant woman has a large number of genital
warts, the growths can complicate a vaginal delivery. If the warts block the birth
canal, the woman may need a cesarean section. 

Chlamydia is the most commonly
reported STI that can be easily treated in the U.S. It can affect both men and women.
This infection may cause an abnormal genital discharge and burning with urination.
In
women, untreated chlamydia may lead to pelvic inflammatory disease (PID). Chlamydia
can be treated with antibiotics. Unfortunately, many people with chlamydia have few
or no symptoms of infection. The most common and serious complications occur in
women. In addition to PID, these include tubal (ectopic) pregnancy and infertility.
Chlamydia can also be carried in and affect the rectum. If you are pregnant and have
chlamydia, the infection can be passed to your baby at birth. This can cause eye
infections or pneumonia in your baby. With chlamydia, you are also more likely to
have your baby too early. 

Gonorrhea may be present but
cause no symptoms. Or it can cause a discharge from the vagina, penis, or rectum,
painful or difficult urination or bowel movements, or a sore throat that doesn’t go
away. The most common and serious complications happen in women. They include PID,
tubal pregnancy, and infertility. Men can also get infection of the prostate or
epididymis. Gonorrhea can be treated with antibiotics. Gonorrhea can also be carried
in and affect the rectum. Gonorrhea at the time of childbirth can spread to the baby
and cause severe eye infection. 

Genital herpes infections are
caused by the herpes simplex virus (HSV). Symptoms may include painful blisters or
open sores in the genital, buttock, or rectal area. Tingling or burning sensation
in
the legs, buttocks, or genital area may happen just before the blisters show up. The
herpes sores usually disappear within a few days. The virus stays in the body for
life, and the sores may return from time to time. There is no cure for HSV. But
medicine can shorten an outbreak and ease symptoms. It can also be used to prevent
outbreaks. HSV can be passed on from the mouth to the genitals during oral sex. The
virus can be passed on to sexual partners even if the person has no visible blisters.
This is from so-called asymptomatic shedding of the infection. HSV can also be spread
to a baby at the time of childbirth. This causes a very severe infection in the
baby. 

The first symptom of syphilis is
a painless open sore that usually shows up on the penis, in the vagina or mouth, or
on the skin around the rectum or genitals. Untreated syphilis may go on to more
advanced stages. These include a rash. Over time it can cause problems with the heart
and central nervous system. Syphilis can be treated with antibiotics. If a pregnant
woman has untreated syphilis, the disease can cause dangerous, even fatal, problems
for the baby. The way congenital syphilis affects the baby depends on how long the
woman has had the disease and if or when she was treated for the infection. This form
of syphilis can cause miscarriage, stillbirth, or death of the baby shortly after
birth. Untreated babies that do survive will likely develop serious multiple organ
problems of the brain, heart, eyes, and ears.

Other diseases that may be
sexually transmitted include:

• Bacterial vaginosis

• Chancroid

• Molluscum contagiosum

• Pubic lice

• Scabies

• Trichomoniasis

• Vaginal yeast
  infections