According to the Centers for Disease Control, the men were told they were being treated for "bad blood"—a colloquialism describing various conditions such as fatigue, anemia and syphilis—which was a leading cause of death among southern African-American men.The 40-year study became a textbook example of poor medical ethics because researchers had knowingly withheld treatment with penicillin and because the subjects had been misled concerning the purposes of the study. The revelation in 1972 of these study failures by a whistleblower, Peter Buxtun, led to major changes in U.S. law and regulation on the protection of participants in clinical studies. Now studies require informed consent, communication of diagnosis, and accurate reporting of test results. Similar experiments were carried out in Guatemala from 1946 to 1948. It was done during the administration of American President Harry S. Truman and Guatemalan President Juan José Arévalo with the cooperation of some Guatemalan health ministries and officials. Doctors infected soldiers, prostitutes, prisoners and mental patients with syphilis and other sexually transmitted infections, without the informed consent of the subjects, and treated most subjects with antibiotics. The experiment resulted in at least 83 deaths. In October 2010, the U.S. formally apologized to Guatemala for the ethical violations that took place. Secretary of State Hillary Clinton and Health and Human Services Secretary Kathleen Sebelius stated "Although these events occurred more than 64 years ago, we are outraged that such reprehensible research could have occurred under the guise of public health.
Many people who present with secondary syphilis (40–85% of women, 20–65% of men) do not report previously having had the classical chancre of primary syphilis. Latent
Latent syphilis is defined as having serologic proof of infection without symptoms of disease. It develops after secondary syphilis and is divided into early latent and late latent stages. Early latent syphilis is defined by the World Health Organization as less than 2 years after original infection. Early latent syphilis is infectious as up to 25% of people can develop a recurrent secondary infection (during which spirochetes are actively replicating and are infectious). Two years after the original infection the person will enter late latent syphilis and is not as infectious as the early phase. The latent phase of syphilis can last many years after which, without treatment, approximately 15-40% of people can develop tertiary syphilis. Tertiary
Tertiary syphilis may occur approximately 3 to 15 years after the initial infection, and may be divided into three different forms: gummatous syphilis (15%), late neurosyphilis (6.5%), and cardiovascular syphilis (10%). Without treatment, a third of infected people develop tertiary disease. People with tertiary syphilis are not infectious.Gummatous syphilis or late benign syphilis usually occurs 1 to 46 years after the initial infection, with an average of 15 years. This stage is characterized by the formation of chronic gummas, which are soft, tumor-like balls of inflammation which may vary considerably in size. They typically affect the skin, bone, and liver, but can occur anywhere.Cardiovascular syphilis usually occurs 10–30 years after the initial infection.