What is the most common STI among young adults today?

Chlamydia is the most common STI among teenagers & young adults. Approximately 80-90% of women who have chlamydia, have no symptoms ever. It is also uncommon for men to have symptoms -- only about 30% of them do. The second most common STI is HPV or the human papilloma virus, which is the virus that can lead to genital warts. Some types of HPV also cause cervical cancer in women and cancer of the penis in men. With HPV, like chlamydia, there are usually no symptoms and that is why it is important to get checked. In one study done by UC Berkeley 50% of the women tested were positive for HPV yet had no symptoms and were unaware that they had the virus.