In this study, a systematic review was undertaken to address the objective of the study. These reviews are an ideal tool for determining the scope of a set of publications on a given topic. They indicate the volume of publications and studies available. In addition to acquiring a global vision of the documents, the reviews allow researchers to evaluate, synthesize, and critique the evidence inherent to the objective of the study (McFarlane, 1988; Munn et al., 2018). The Dialectical Structural Model of Care (DSMC) (Siles González, 2005) has been used because of its relevance in delving into the cultural and social roots of structures that are particularly linked to sexual and gender diversity, as opposed to the binary dimension. This model identifies the functional dynamics of structures, allowing the analysis of the causes that lead to their changes.

The Multiple Event Detection and Classification (MEDC) methodology is based on structures that serve as support for the process of ordering and analyzing the data. In this research, its application is important due to the social, cultural, and care study in which we are involved. Therefore, the structures applied to it are the following: (1) functional unit (F.U), where the origin of sexual and gender minorities in the various social systems that determine sexual and gender diversity, other than the binary dimension, is addressed; (2) functional framework (F.M), related to sexual and gender minorities within the social context; and (3) functional element (F.E), which in this case reflects the relationship between sexual and gender minorities and syphilis. These structures utilize a suitable tool for the organization and analysis of the data since the aim is to obtain a vision of the historical phenomena from the perspective of cultural history (Siles González, 2004). Within this study, three thematic blocks were developed centered on the MEDC; each one of them encompassed the structures that make up this historical and cultural model (Siles González and Solano Ruiz, 2016) (Figure 1).

The process of a systematic review started with an exploratory research question (Peters et al., 2015) aimed at synthesizing and systematically critiquing existing knowledge (Colquhoun et al., 2014). This review involved several steps (Levac et al., 2010).

Initially, the topic was identified, and a research question was established, which was posed within the cultural history and the culture of caregivers using the Dialectical Structural Model of Care (DSM): How were relationships between people with sexual and gender diversities, and syphilis established? The following inclusion criteria were considered: (1) publications in Spanish, English, Portuguese, and French; (2) no time restriction for publication (as this was historical research); (3) subject matter related to sexual and gender diversities; and (4) thematic selection based on the importance and relevance of the topic, as well as the development and influence of homosexuality throughout history. The exclusion criteria included the following: (1) repeated publications; (2) abstracts, editorials, chapters and books, theses, dissertations, and course completion papers; and (3) studies not related to the proposed topic.

The search for documentation was carried out between January and July 2022 by physically visiting the Library of the University of Castilla-La Mancha, the National Library of Spain, the Library of Castilla-La Mancha (Alcázar de Toledo), the National Historical Archive, the CSIC Library, and the World Digital Library (UNESCO). Several databases were consulted, including the following: (1) Latin American Health Bibliographic Database (CUIDEN); (2) PubMed; (3) Scopus; (4) Science Direct; and (5) Google Scholar. MeSH and DeSH terms were used to carry out a more exhaustive and advanced search using the Boolean operators “[AND]” and “[OR]”. Additionally, even word-word combinations were used where appropriate to reflect the syntax and search rules common to individual databases. The descriptors were as follows: sexual and gender minorities, transgender persons, gender diversity, syphilis, sexuality, and history of nursing. Due to the diversity of data collected from newspapers, books, digitized documents, and manuscripts, the research corpus was composed of a set of documents containing the core phrase. For the analysis of this corpus of documents, a flow chart was constructed following the PRISMA strategy, which allowed a synthesis of the information provided by each document and, consequently, the analysis of the data (Figure 2).

The documentary analysis was carried out systematically following the objective of the study. The steps followed in the analysis were as follows: (1) thematic linking; (2) preliminary classification of the documents based on inclusion and exclusion criteria; (3) selection of relevant information; and (4) interpretation and comparison of the results. The selected material was analyzed from the point of view of the three thematic blocks of study, each of them encompassed in the DSMC structures. These included the following: (1) the origin of sexual and gender minorities; (2) sexual and gender minorities within the social context; and (3) sexual and gender minorities and syphilis. The first, second, and third authors carried out general data collection. The fourth author examined the findings in depth, and the fifth and sixth authors identified the thematic blocks under the DSMC structures of functional unit, functional framework, and functional element. Discrepancies were resolved by consensus among the researchers.

Currently, there is no agreement on the origin of homosexuality. Some researchers believe that, in primitive civilizations, it was accepted and permitted as part of the idiosyncrasies of human beings in those civilizations (essentialist current), while other researchers consider homosexuality to be a social construct introduced in the Middle Ages because of the existing dichotomy between homo-social and hetero-social relationships (constructionist current) (Solana, 2018).

Current essentialist scholars argue that, in Egypt, Greece, and Rome, interpersonal relationships were allowed as long as they satisfied the pre-established moral canons and adapted to the rational ethical principles and social convictions of the time, even if they only appeared to be in conformity and the true motive of the relationship was hidden (Pulecio Pulgarin, 2009). Plato, in his work, The Banquet, states that it is possible to understand that there are men who sexually seek other men, women who prefer sexual contact with women, and men who desire women and women who desire men (Solana, 2018).

However, current constructionist scholars argue that the concept of homosexuality emerged in the West during the 12th and 13th centuries. According to them, closed communities of men existed where intimate coexistence between members was the backbone of a homo-social relationship. Such relationships fostered virile friendships, whose masculine ideal was the warrior, a man who lived apart from women (Soto Buenaventura, 2021).

During these centuries, feudal society promoted the male-female love relationship, and sexual practices were oriented toward the lady's gallantry, even though the woman was considered a commodity, the property of the masters, the father, and the husband. With gallantry came the concept of courtly love, the basis of the troubadours' lyrics, which exalted the permanent suffering of the lovers in their impossible love and passion and where the love relationship went beyond good and evil. Consequently, the dichotomy of homosexual relationships and heterosexual relationships emerged during the 12th and 13th centuries (Di Gerónimo, 2012).

The Christian Church, between the Second Lateran Council of 1139 and the Fourth Lateran Council of 1212, attempted to weaken the existing exaltation of love within the closed communities of the religious orders. This led to the persecution of marriages and concubinages of priests, deacons, sub-deacons, monks, and nuns. Adulthood was viewed as a sin since male-female love was only allowed within the conjugal framework. Further, with the intention of limiting homo-social relationships within religious orders, he introduced the accusation of sodomy to condemn any loving relationship that was not male-female. Incidentally, the term sodomy comes from the story of Sodom and Gomorrah in the Old Testament (Soto Buenaventura, 2021).

During the 13th and 14th centuries, the Catholic Church, through the tribunal of the Holy Inquisition, tortured people in same-sex relationships accused of sodomy and condemned them to death at the stake for being guilty of a nefarious sin. Such persecution was widespread until the 18th century (Boswell, 1998; Torquemada Sánchez, 2014).

In 17th and 18th century England and France, people in same-sex relationships gathered in so-called fun houses— places where social and sexual norms were challenged—as pleasure was at its peak and there was unbridled passion (Cancino Barffusón, 2012). However, to get around the accusation of sodomy, euphemistic expressions such as libertine, romantic friendship, Malthusian partner, and sexual invert were used. Sexual attraction was considered an autonomous biological and psychic instinct (Foucault, 2008; Cancino Barffusón, 2012). In his play, The Bostonians, Henry James recreated an emotional union between two independent women, which gave rise to the term “Boston marriage” (Alventosa del Río, 2008; Beteta Martín, 2012). During this time, only the term “homo-social practices” existed, for it was not until 1869 that the term homosexual was coined to refer to a specific type of person (Cancino Barffusón, 2012).

In the 19th century, people in same-sex relationships began to be targeted for their gestures, their manners, their way of dressing, and their anatomy, morphology, and facial expressions (Foucault, 2008). With the advent of sexology, homosexuality was considered a pathological disorder. As a result, the person who felt affective and sexual attraction for a person of the same sex and behaved in an unconventional way was treated with therapeutic techniques of little validity. With the rise of totalitarian regimes in the 20th century, homosexuality came to be persecuted and strongly repressed, and people in same-sex relationships were considered a danger to society. In this context, lesbianism was considered a disease among female prostitutes (García Valdés, 1980; Alventosa del Río, 2008). With the first surgical interventions on transsexuality, a sub-specialty emerged within sexology whose purpose was to attend to the needs of transsexuality (Beteta Martín, 2012) (Table 1).

Following the spontaneous emblematic moment of homosexuality that occurred in the early hours of 28 June 1969 in the Stonewall Inn (New York), stigmatization, discrimination, and homophobia have been combated. The Stonewall riots that followed are often cited as the first instance when the gay community fought against a system that persecuted non-normative people (Cancino Barffusón, 2012).

The repression of certain types of sexual behavior in both private and public life began in feudal Europe. A redefinition and updating of social values followed, which led to the persecution of behavior that violated pre-established norms. Those who challenged the values and/or deviated from pre-established norms were called heretics and known as sodomites in the 13th century. They were the target of intolerance and persecution, resulting in the phenomena of interpersonal violence, such that anyone whose behavior deviated from Christian morality was socially marginalized during the 14th and 15th centuries (Bazán Díaz, 2007).

In an intolerant society, as described above, people who were rejected or persecuted for their sexual behavior for centuries lost their rights to develop their human potential and were forced to repress their feelings for fear of being denounced or scrutinized by people whose recognition or social position gave them power (Porras Gallo, 2002).

The demographic growth of the 19th century, a consequence of the Industrial Revolution, produced suburbs on the outskirts of cities inhabited by a diverse group of people, including those marginalized by their sexual behavior. This gave rise to slums or Chinatowns—population nuclei where people lived in overcrowded conditions—with precarious economic means and with the need to seek daily sustenance. The only recourse for men and women in these places who intended to improve their economic condition was practicing prostitution (Porras Gallo, 2002; Huard, 2016).

In Spain, during the Franco dictatorship, prostitution (both male and female) was the economic engine of these neighborhoods despite police controls. The homophobic discourse was developed during this period with the approval of the Church and state institutions. Anyone whose gender identity did not fit the heterosexual model was forced to hide and repress their feelings to the point of becoming invisible for fear of being arrested for public scandal, as homosexuality was criminalized as per the 1954 Law on Vagrants and Thugs. This law was enacted with the aim of curbing and controlling prostitution (Huard, 2016; Díaz, 2019).

Consequently, venereal disease among the homosexual population was kept a secret, especially in Chinatown, which provided discretion and a certain level of tolerance toward permissive behavior, making it easier for the homosexual community to take refuge there. However, affluent members of the homosexual population met in more sanitized and hygienic environments. As a result, the Drugstore in Barcelona's Gracia district and Madrid's Chueca district emerged as popular gathering places for the homosexual community. Today, these areas are acknowledged for their association with homosexuality, where it still remains an integral part of the respective neighborhoods (Herrero-Brasas, 2001; Díaz, 2019) (Table 2).

The Law on Vagrants and Thugs was selectively applied with class criteria since individuals in homosexual relationships belonging to powerful families were excluded from it. Therefore, a very high number of those judged by the courts of the time for homosexuality belonged to the most disadvantaged social groups; it was exceptional for someone belonging to the upper social class to be sentenced to prison for homosexuality (Herrero-Brasas, 2001; Huard, 2016; Díaz, 2019). The Law on Vagrants and Thugs was repealed on 4 August 1970 and replaced by the Law on Dangerousness and Social Rehabilitation, which remained in force until 26 December 1978. However, the homosexual community was no longer convicted under this law, though they could be arrested under the Public Scandal Act. People with sexual and gender diversity, different from the binary dimension, did not stop being persecuted until 26 December 1978, when the first president of democracy, Adolfo Suárez, signed a modification of the Law of Dangerousness and Social Rehabilitation, which eliminated homosexuality from its text, thus decriminalizing it in Spain (Herrero-Brasas, 2001).

In his writings, Hippocrates describes a disease associated with vagrancy, overcrowding, immorality, and a lack of hygiene, which is similar to the symptoms of syphilis. However, some researchers believe that syphilis arrived in Europe after Columbus' third voyage in 1493; on arriving in Spain, Columbus reported that one of his crew members had contracted an infection on the island of Hispaniola (Frith, 2012). The first known treatment for syphilis consisted of the following: applying guaiac resin, meticulous removal of the syphilitic patient's secretions from their lesions, and applying mercury preparations by the active rubbing of the patient's skin with a Neapolitan ointment or gray ointment (Leitner et al., 2007). The discovery of the causative agent of syphilis in 1905 by Fritz Schaudin and Erich Hoffman marked the beginning of effective treatment for this disease. August von Wassermann's understanding of the humoral reaction for the serological diagnosis of syphilis in 1906 furthered progress in this field. Alexander Fleming's discovery of the Penicillium notatum bacterium in 1928 also contributed to the advancement of treatment for syphilis. These three milestones changed the course of the disease (Ros-Vivancos et al., 2018).

Syphilis was the cause of death of great music composers, scientists, and politicians who were associated with prostitution and homosexuality. Discretion over this influenced the spread of the most non-visible stages of the disease. Therefore, in the 19th century, with the understanding of the importance given to hygiene, attempts were made to regulate prostitution, even advocating its abolition, while any manifestation of homosexuality was strongly repressed. During the first half of the 20th century, there was strict sanitary control of brothels. Meanwhile, medical treatises of the time supported sex education following Judeo-Christian morality with the intention of eradicating syphilis and, at the same time, promoting sexual relations within the conjugal framework. However, even with this tight control, syphilis was not eliminated among the heterosexual or homosexual population (Ros-Vivancos et al., 2018).

The discovery of penicillin and the control of prostitution considerably reduced the prevalence of syphilis and the incidence of the more serious forms of the disease, such as cardiovascular syphilis, neurosyphilis, and congenital syphilis. However, the disease continues to be called the great simulator because every 10 years or so, there are upturns in incidence. Therefore, with the sexual revolution, a widespread use of contraceptives, the liberalization of homosexual relations, and injecting drug use, syphilis continues to be a worldwide problem among the heterosexual and homosexual populations (Capdevila and Fernández, 2007) (Table 3).

The general objectives of syphilis prevention and control are to reduce the incidence of this infection, to promote early diagnosis to prevent associated comorbidities, and to reduce discrimination against people suffering from this pathology (Palacios Muñoz et al., 2006; Repiso et al., 2009). In Spain, it is difficult to encourage a person for diagnosis among the heterosexual population, but it is almost impossible among the homosexual population, especially when syphilis is perceived as a social stigma, and the infected person does not present symptoms that would make it necessary to carry out a diagnostic test. These two factors, together with the difficulty of accessing resources, the lack of information, and the inconvenience of contact tracing, mean that the chain of transmission is not stopped, and syphilis goes undetected in the heterosexual and homosexual populations (Ministry of Health, 2021).