What is the most common STD among college students?

Chlamydia
I work in the UK in a seaside town on the North West coast of the country not far from Manchester and Liverpool. My job title is "Young Mens Sexual Health Outreach Worker" and a part of that role we work to screen young people in schools and colleges for Sexually Transmitted Infections. I can tell you that almost 60% of young people who have HAD SEX WITHOUT A CONDOM (and therefore are most at risk) and opt for a STI screen have the STI Chlamydia. It is so common as it has very few symptoms - 70% of females and 50% of males have no symptoms or very mild symptoms. It is very easy to transmit - if you do not use a condom during intercourse. However, it is very easy to test for and treat - a simple urine test and a course of antibiotics are enough to ascertain and get rid of the infection. If left untreated Chlamydia will lead to infertility and expensive health bills in the future - hence the Government feels the need to treat this STI as seriously as it does. And I don't think they're wrong either.