Screening for other sexually transmitted infections, including syphilis and HIV, is important when you've been diagnosed with a new chlamydia infection.
Having a sexual relationship with one partner (monogamous) who is not infected is one way to avoid chlamydia. The proper use of condoms during intercourse usually prevents infection.
McCormack WM. Urethritis. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 106.