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A sexually transmitted infection (STI) is any infection that is acquired through sexual contact. There are more than 25 infectious organisms known to be transmitted primarily through sexual intercourse, including anal and oral sex. STIs may also be spread through blood contact, including the sharing of needles. The term sexually transmitted infection (STI) is a more encompassing term than sexually transmitted disease (STD), as some infections may not cause any symptoms and may be curable. If the infection results in alteration of the typical function of the body, it is then termed a disease. For the purposes of this chapter, these two terms will be used interchangeably.

STI Epidemiology in the United States

The Centers for Disease Control and Prevention (CDC) estimates that on average there are 20 million new STIs diagnosed in the United States each year at cost of approximately $16 billion (Owusu-Edusel et al, 2013). Half of these cases are diagnosed in people aged 15–24 years (Satterwhite et al, 2013). According to the CDC’s publication Sexually Transmitted Diseases Surveillance, 2015, the year 2015 was remarkable for the highest annual number of chlamydial infections ever reported—more than 1.5 million cases. In addition, the combined reported number of cases of chlamydia, gonorrhea, and syphilis (primary and secondary) reached a record high in 2015. From 2014 to 2015, the syphilis rate rose 19%, the gonorrhea rate rose 13%, and the chlamydia rate rose 6%. Chlamydia and gonorrhea rates continued to be highest amongst the 15–24-year-old age group, while the syphilis rate increased most among homosexual men (CDC, 2016). Unfortunately, despite increasing STI incidence in the United States, funding is decreasing for state and local STI programs. It is estimated that around 20 state and local STI programs closed in 2012 due to budget cuts leading to reduced clinical hours, contact tracing, and STI screening. If this trend continues, more STIs will go undiagnosed and untreated (Owusu-Edusel et al, 2013).

What caused this dramatic rise in reported STI rates? The apparent increase might reflect improved STI reporting, improved detection, or improved access to care. Alternatively, the increase could represent a true incidence in STI rates, which suggests decreased utilization of safer sex practices. The increase might also reflect decreased federal and state funding for STI education and prevention. The answer to this question remains unknown and largely speculative.

It has also been suggested that amplified communication networks, widespread social media, and ever-increasing employment of internet dating tools may contribute. Organizations including UNICEF in the Asia-Pacific region, the AIDS Health Foundation, and state and local governments in the United States have inferred that mobile dating applications may be responsible for the rapid increase in STI rates worldwide. These websites are thought to create an environment that facilitates unprotected, impulsive sexual encounters leading to increased rates of STIs (UNICEF, 2015). No studies have been conducted to substantiate these claims.


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