Before 1970, “venereal disease” (VD) was the nearly universal term for the medical conditions of interest to our specialty. It referred more or less exclusively to syphilis, gonorrhea, and the less common lymphogranuloma venereum, chancroid, and donovanosis. Nongonococcal urethritis (NGU) and vaginal infections like trichomoniasis, anogenital warts, and “herpes progenitalis” were understood to be associated with sexual activity, but for the better part of a century, their sexual transmission was a matter of debate, partly because they were common in people who seemed to be at low risk for VD.
“Sexually transmitted disease” (STD) became the norm in the 1970s, reflecting acceptance of the evidence for sexual transmission of nontraditional disorders and of emerging pathogens like Chlamydia trachomatis, as well as growing sensitivity to the pejorative connotations of “VD”. There was also increasing awareness that all these were prevalent in the “general population,” including people at low risk for the traditional infections and implying, at the time, persons thought to be more responsible in their sexual behavior than those with VD. Then the 1980s saw the introduction of “sexually transmitted infection” (STI). We learned that most chlamydial infections, genital herpes, trichomoniasis, and even many gonococcal infections were subclinical. Most infections caused few or no symptoms and seemed harmless, and serious complications were believed to be infrequent—that is, disease seemed to be an uncommon consequence. Even asymptomatic infection with human immunodeficiency virus (HIV) was considered distinct from overt acquired immunodeficiency syndrome (AIDS), and for a decade, it was common to inform patients that they “only” carried the virus and did not have AIDS.
Time and improved knowledge have undercut this rationale for STI. There is clearer understanding of the often serious outcomes of outwardly silent infections, such as progressive immunodeficiency caused by HIV, enhanced HIV transmission because of asymptomatic type 2 herpes simplex virus and other genital infections, infertility due to inapparent chlamydial infection, and dysplasia and cancer caused by otherwise asymptomatic human papillomavirus infections. Arguably, therefore, most of these are properly viewed as diseases as well as infections. Furthermore, an evolving hypothesis is that some cases of etiologically obscure NGU, cervicitis, and vaginal discharge might not be infections in the usual sense, that is, caused by defined pathogens, but transient responses to perturbation in the microbiome after exposure to partners’ genital or oral flora, or perhaps as a consequence of sexual activity itself.
The other rationale for “STI” was that some patient advocates came to consider “disease” to be more pejorative than “infection”, and to view “STD” in a similar light as “VD” in past decades. In the United States, this perspective and use of “STI” seem to be especially common among reproductive and women’s health providers, whereas “STD” remains in dominant use by public health agencies and clinicians in categorical STD clinics, perhaps reflecting differences in the proportions of patients with overt symptoms and signs in different clinical settings. However, there is room for debate about differing connotations of the two words. To my knowledge, no reported research has studied whether infected persons or those at risk interpret “disease” and “infection” differently. It may be the case, but it seems to me a soft one. (Such a study would be quite simple, inexpensive, and very welcome.)
Today, STD and STI should be considered synonymous and interchangeable. The former British Journal of Venereal Diseases was renamed Genitourinary Medicine and then Sexually Transmitted Infections, and the venerable International Union against the Venereal Diseases and Treponematoses became the International Union against STI. On the other hand, the American STD Association (originally the American VD Association) retains its name, as do its journal Sexually Transmitted Diseases, the National Coalition of STD Directors, and the Centers for Disease Control and Prevention’s Division of STD Prevention. Those who prefer either term should use it freely, with neither defensiveness nor pride in either one. If the microbiome hypothesis of the etiology of some syndromes is confirmed by current and planned research, perhaps someday we should consider “sexually transmitted disorders” as an all-encompassing term. In that case, “STD” may carry the day!