Final answer:
HPV is the most common viral STI in the United States. It leads to many infections each year and can be prevented with vaccines like Gardasil®.
Step-by-step explanation:
The most common viral STI is HPV (Human Papillomavirus).
Explanation
Sexually Transmitted Infections (STIs) are common and can be caused by bacteria, viruses, parasites, and fungi. Among these, viral STIs are notable because, unlike bacterial STIs, they cannot generally be cured and can lead to long-lasting health issues. Viral STIs include infections such as genital herpes, hepatitis B, and HIV/AIDS. However, the most common viral STI in the United States is HPV. With an estimated prevalence of 79.1 million infections in 2008, HPV far surpasses other viral STIs in terms of the number of people affected.
HPV is particularly significant due to its association with severe health problems, including cervical cancer. Vaccines, such as Gardasil®, can prevent most HPV infections. The Centers for Disease Control and Prevention (CDC) recommends vaccination for females and males starting at ages 11 or 12, although the vaccine can be given as early as age 9 and up to age 26.
While HPV is the most common viral STI, it's important to note that chlamydia is actually the most common STI overall in the United States, but it is caused by a bacterium, Chlamydia trachomatis, making it the most common bacterial STI. Chlamydia and other bacterial STIs, such as gonorrhea and syphilis, are treatable with antibiotics, a stark contrast to viral STIs which, as already stated, lack definitive cures and are managed through symptom control, prevention, and monitoring.