Half of all STI diagnoses occur in adolescents and young adults between the ages of 15 and 24 years. Many people with STIs are asymptomatic or experience only mild symptoms of infection. Without testing, people infected with STIs may unknowingly spread the infection to others. STIs can lead to serious health complications, so appropriate STI screening and diagnosis is a major public health concern. STI can be due to infection by a wider spectrum of microbes (viruses, bacteria, parasites, and fungi), However, the most common causes of STI are Chlamydia (Chlamydia trachomatis), Gonorrhea (Neisseria gonorrhoeae), Mycoplasma henitalium, Gardnerella vaginalis, Trichomoniasis (Trichomonas vaginalis), Herpes Simplex 1 and 2, Ureaplasma (urealyticum and parvum), Haemophilus ducreyi, HPV (human papillomavirus 16, 18, & 45) and Syphilis (Treponema pallidum).