What are Sexual Transmitted Infections (STIs)?

STIs are infections that spread by physical contact during vaginal, anal, or oral sex. The microbes that cause sexually transmitted diseases are equal opportunity bugs. There are 2 major categories of STIs – bacterial (caused by bacteria) and viral (caused by viruses). Bacterial STIs are often cured with antibiotics; whereas viral STIs have no cure but their symptoms can be alleviated or slowed with treatment. A third category, STIs caused by protozoa (trichomoniasis, crabs/pubic lice, scabies) also exist and are cured with antibiotics and topical creams.

One of the most common symptoms of an STI is no symptoms at all so it’s important to go for check-ups. 80 percent of women and 40 percent of men diagnosed with chlamydia may not experience symptoms. STIs need to be diagnosed correctly and fully treated as soon as possible to avoid complications that could be serious and/or permanent.

Bacterial STDs


  • Chlamydia is one of the most widespread bacterial STDs in the United States. The Centers for Disease Control and Prevention (CDC) estimates that more than 3 million people are infected each year.


  • In 2002, 351,852 cases of gonorrhea were reported to the Centers for Disease Control and Prevention (CDC). In the United States, approximately 75 percent of all reported cases of gonorrhea are found in people aged 15 to 29 years. The highest rates of infection are usually found in 15- to 19-year old women and 20- to 24-year-old men.


  • Syphilis is a sexually transmitted infection (STI), once responsible for devastating epidemics. It is caused by a bacterium called Treponema pallidum. The rate of primary and secondary syphilis in the United States declined by 89.2 percent from 1990 to 2000. The number of cases rose, however, from 5,979 in 2000 to 6,103 in 2001. The U.S. Centers for Disease Control and Prevention reported in November 2002 that this was the first increase since 1990.

Viral STDs

Human Papillomavirus and Genital Warts (HPV)

  • Health experts estimate there are more cases of genital HPV infection than any other STI in the United States. According to the American Social Health Association, approximately 5.5 million new cases of sexually transmitted HPV infections are reported every year. At least 20 million people in this country are already infected.


  • Nationwide, since the late 1970s, the number of people with genital herpes infection has increased 30 percent. The largest increase is occurring in young teens. HSV-2 infection is more common in three of the youngest age groups which include people aged 12 to 39 years.

Human Immunodeficiency Virus (HIV)

  • HIV is a virus that weakens a person’s immune system by destroying important cells that fight disease and infection. No effective cure exists for HIV. But with proper medical care, HIV can be controlled. According to the CDC, an estimated 1.2 million Americans over the age of 13 are living with HIV.


  • There are currently three different strains (A, B, and C) of the hepatitis virus. Although there is no cure, early detection and proactive treatment is key to for these STIs. A vaccine also exists for Hepatitis A and B.

Molluscum Contagiosum

  • Molluscum contagiosum is a skin infection caused by a virus. This infection causes bumps on the skin. It often occurs in children but is also considered a sexually transmitted disease in adults. The bumps will disappear on their own after several weeks to months.