STDs as Emerging Infections

STDs are not a stationary group of infections and syndromes. Eight new sexually transmitted pathogens have been identified since 1980, bringing with them new challenges to prevention and treatment (Table 2-2). The most well-known of the recently described STDs is HIV infection. Since HIV-1 was found to be the cause of virtually all cases of AIDS in the United States in the mid-1980s, a closely related retrovirus, HIV-2, and a more distantly related pair of retroviruses, human T-lymphotrophic virus types I and II (HTLV-I, -II), have been shown to be sexually transmitted as well. In addition, in 1995, scientists confirmed and identified human herpes virus type 8 as a likely sexually transmitted virus and a possible cause of Kaposi's sarcoma and body cavity lymphomas (Chang et al., 1994). In contrast to newly recognized viral STDs, some bacterial STDs, such as syphilis and gonorrhea, have been documented for centuries and have recently reemerged in the United States along with a spectrum of barriers to prevention (Wasserheit, 1994). As demonstrated by the recent finding that bacterial vaginosis in pregnant women increases the risk for premature delivery of a low-birth-weight infant (Hauth et al., 1995; Hillier et al., 1995), the full clinical spectrum of many STDs is still being described. In addition, for many previously described pathogens, such as hepatitis B virus and cytomegalovirus, it has become evident that a major route of adult transmission—often the major route—is sexual. Further, new research shows that many common diseases of previously unknown cause, such as cervical dysplasia, are in fact caused by newly described sexually transmitted pathogens.

These examples of emerging infections (IOM, 1992) make it clear that more STDs will emerge and become established in the United States. This is because of increasing global travel and worsening ecological pressures, such as population

Table 2-2 Sexually Transmitted Pathogens Newly Identified or Newly Recognized as Sexually Transmitted, and Associated Syndromes, 1980-1995

Sexually Transmitted Agent

(year identified or recognized)

Associated Syndromes

Human papillomaviruses (1976-present)

Genital and anal warts, dysplasias, and cancers

HTLV-I (1980)

T-cell leukemia/lymphoma; tropical spastic paraparesis

HTLV-II (1982)

Unknown

Mycoplasma genitalium (1981)

Nongonococcal urethritis

Mobiluncus sp. (1980, 1983)

Bacterial vaginosis-associated

HIV-1 (1983)

AIDS

HIV-2 (1986)

AIDS

Human herpes virus type 8 (1995)

Kaposi's sarcoma; body cavity lymphoma



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