What is chlamydia and how common is it?

Chlamydia (pronounced kluh-mid-ee-uh) is the most frequently reported sexually transmitted disease (STD) caused by bacteria (Chlamydia trachomatis) in the U.S. An estimated 2.8 million Americans get chlamydia each year. Women are often reinfected, meaning they get the STD again, if their sex partners are not treated. Reinfections place women at higher risk for serious reproductive health complications, including infertility.