Sexually transmitted disease (STD) is the term used for diseases that are transmitted through human sexual activity. However, some STDs are also transmitted through body fluids, such as blood and through contaminated IV drug needles. Sometimes STDs are also referred to as Sexually Transmitted Infections (STI), but STI is a broader term than STD. STI includes asymptomatic infections, where persons are infected with the organism, but do not show any symptoms or signs of an illness or a disease. STI have been well known for hundreds of years in medicine. The branch of the medicine that studies treatment and prevention of STD or STI is called venereology.
Sexually transmitted diseases remain a major public health problem around the globe, including underdeveloped countries in Asia or Africa and developed countries like the United States. In the U.S., STDs are one of the most critical health challenges with estimated 19 million new infections every year with the health care cost of $17 billion . STDs indeed lack easy solutions since they are primarily associated with human behavior. However, prevention of spread of STDs has been studied well and has shown to be effective in a various population. STDs are most commonly caused by viruses and bacteria, but some fungi or parasites can cause STD as well.
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