All of them are very serious and some even life threatening.
HIV/AIDS is the hardest to treat because the virus mutates at a very high rate, and it has killed more people than any other STD.
Chlamydia, a bacterial infection, is more infectious than any other STD.
HIV
HPV
Gonorrhea most likely.
melanoma
Its a type of STD
Yes - PID is a serious condition caused by an untreated STD.
Type A is the most common form of NPD and the most serious, with death usually occurring by the age of 18 months.
Trichomoniasis is the most common protozoan STD in the US. Aside from giardia, which is rarely sexually transmitted, it's the only protozoan STD.
its a type of STD
more serious and most serious
Syphylis
Chlamydia is the most common bacterial STD in the US, and the most common reportable STD. You should know that not all STDs are reportable, so the CDC doesn't get direct reports about HPV or trichomonas.