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Oral Sex and STDs

Over the last few years print and audiovisual media stories have underscored a widespread interest in as well as spawned general confusion about the topic of oral sex. This month’s Sexual Health Update defines oral sex, outlines a general picture of how common the practice is among American adults and youth, and briefly inventories the sexually transmitted diseases transmissible via oral sex.

The transmission of fecal-oral and respiratory pathogens such as hepatitis A, Shigella species and Neisseria meningitidis is not discussed; readers are referred to two excellent reviews by Edwards and Carne that address these topics – (Sex Trans Infect. 1998;74:6-10 and Sex Trans Infect. 1998;74(2):95-100.) 1 2

Additionally, a review that addresses whether condom use provides any risk reduction benefits during oral sex has never been published and is beyond the scope of this article. Oral sex can be defined as contact of one person’s mouth (active) with the genitals of another person (receptive). Although the practice of oral sex may not affect someone’s virginal status in the traditional meaning of the term virgin (ie, someone who has not had penile-vaginal intercourse) oral sex is sex, and is not part of the repertoire of abstinent behavior.

Oral sex is likewise neither “safe” nor “safer” sex. With the major exception of pregnancy, the panoply of risks associated with the practice of oral sex roughly mirror those associated with penile-vaginal sex, though the magnitude of most risks appears to be lessened.

The practice of oral sex is fairly common among adult Americans. In a nationally representative survey of 18- to 59-year olds conducted during the early 1990s, three fourths of respondents said that they had practiced oral sex at some point in their lifetime. One quarter (27%) of men and one fifth of women (19%) said that they participated in oral sex the last time that they had sex. Married men and women were somewhat less likely than their unmarried counterparts to engage in oral sex. African Americans were less likely than Hispanics and whites to practice oral sex.3 The practice of oral sex is similarly not uncommon among adolescents and young adults. A survey of 335 12- to 15-year-olds being seen in health maintenance organizations in the Washington, DC area from 1994-1997 revealed that almost one in five had practiced oral sex, and one quarter of those who had practiced oral sex had never had vaginal intercourse.4 In a separate study of 545 slightly older students – 10th-12th graders – 84% (198/237) of the nonvirgins and 20% (60/308) of the virgins had participated in oral sex.5  High school students in Los Angeles County who consumed alcohol or used recreational drugs were three times more likely than nonusers to engage in oral sex.6 The National Survey of Adolescent Males targets a representative sample of 15- to 19-year-old US males.

Overall, half (49%) of the 1995 participants said that they had participated in oral sex – including three fourths of the nonvirgins and one fifth of the virgins.7 College students are particularly likely to have engaged in oral sex. Though by no means a representative study, of more than 300 sexually active students who volunteered to fill out a questionnaire in class, 86-87% had practiced oral sex.8 Despite the widespread practice of oral sex on college campuses, confusion exists about whether oral sex is sex. In 1994-1995, 1/3 (37%) of 1,101 southern college freshman and sophomores described oral intercourse as abstinent behavior.9

SYPHILIS
First termed syphilis in a 1530 poem about afflicted shepherds, the rampant and severe nature of syphilis in the late 15th century had earlier earned it the moniker the “Great Pox.” Syphilis remained a scourge for centuries to follow, and was exceedingly common across all social strata until the discovery of penicillin. During the preantibiotic era of the early 20th century, 5-10% of autopsies revealed evidence of syphilis, and up to one fourth of persons of low socioeconomic standing were infected.10 Unlike many STDs that cause primarily genital tract infections, syphilis is a systemic (widespread) infection that progresses (if untreated) through typical stages – primary, secondary, latent, and tertiary. Usual symptoms of primary syphilis are a painless ulcer accompanied by lymph node enlargement; the ulcer heals without treatment. About 30% of persons exposed to a partner with a syphilitic lesion will become infected and go on to manifest symptoms of primary syphilis an average of three weeks (range 10-90 days) after exposure. Secondary syphilis causes a flu-like illness accompanied by enlarged lymph nodes and a rash that may go unnoticed. Symptoms are absent during latent syphilis. Tertiary syphilis can affect the nervous system (causing dementia), the cardiovascular system, and soft tissue or bone. Transmission from an infected mother to her infant can also occur during pregnancy and result in congenital syphilis.10
The number of reported syphilis cases decreased 100-fold from 1946 to 2000, from approximately 600,000 cases to just under 6,000. Although an almost 90% reduction was observed from 1990 to 2000, rates began going up in 2001. Women aged 20-24 and men aged 35-39 are most likely to be affected, and rates are highest in African Americans and in persons living in the southeast.11 Oral sex appears to have been an important mode of syphilis transmission in numerous recent outbreaks. Twenty-three of 27 men infected with syphilis in a recent outbreak gave a history of sex with men. Taken together, the 23 estimated that they had had more than 1,400 partners during the previous year, 90% of whom were anonymous. Though not recognized as a risky sexual practice by the infected men, oral sex was the most common sexual practice mentioned.12 In another outbreak, 28 of 30 syphilis cases in an English town over a roughly two-year period were men who had sex with men. The men in this outbreak reported far fewer sexual partners than those in the previously mentioned outbreak – a median of 3 in 6 months. One third (11/30) of infected persons listed oral sex as their only route of acquisition.13 In a third recent outbreak, 39 of 41 reported syphilis cases were men who had sex with men; 19 of the 41
gave a history of only oral sex.14

GONORRHEA
Although the ancient Chinese, Egyptians, Hebrews, Romans, and Greeks recognized the symptoms of gonorrhea (Greek, “flow of seed”) in men, it was a few thousand years before the male and female symptoms were linked. The bacterium Neisseria gonorrhea usually infects “noncornified” skin such as occurs in the urethra, vagina, rectum, mouth, and eye, although not all infections result in symptoms. The overwhelming majority of gonorrhea is sexually transmitted, and mother-to-child transmission can occur during the birth process.15

More than 360,000 cases of gonorrhea were reported to health authorities in the US in 2001, or approximately 130 per 100,000 population. Nationwide, gonorrhea rates generally declined from the mid-1970s through 1997, and have increased slightly since then. Risk, however, varies considerably by age; 15- to 19-year-old women and 20- to 24-year-old men have extremely high rates (703 and 563 per 100,000 respectively for 2001).16

Like its cousin Neisseria meningitidis, Neisseria gonorrhea survives well in the oropharynx (ie, mouth and throat). Although most (90%) pharyngeal (throat) infections cause no symptoms, a sore throat with or without fever and enlarged lymph nodes can accompany infection. Pharyngeal infections resulting from oral sex are quite common, and appear to be more efficiently transmitted from infected male (receptive) to susceptible female (active) than from infected female (receptive) to susceptible male (active). Data also exist to suggest that infected active partners can transmit gonorrhea to susceptible receptive male partners. From 3-7% of heterosexual men, 10-20% of heterosexual women, and 10-25% of homosexual men infected with gonorrhea have pharyngeal infections.17 Of 1,453 STD patients who had throat cultures for gonorrhea,
42 (2.9%) were positive; all 42 gave a history of oral sex. Eleven of the 42 were heterosexual males lacking a recent history of penilevaginal sex, but who had performed oral sex on their female partners. Thirty-five of the 42 were asymptomatic, and 7 had symptoms. All 7 of the patients with sore throat had performed oral
sex on a (receptive) male partner.18

LAMYDIAL INFECTION
With four to five million cases of chlamydial infections reported yearly in the US, chlamydial infections are the most commonly reported conditions in the US. Although authorities estimate that almost 90 million occur worldwide annually, it wasn’t until the early 1970s that practitioners were able to distinguish the genital manifestations of chlamydia from those of gonorrhea.19 Chlamydial infection, caused by Chlamydia trachomatis, can extend from the urethra to the epididymis and from the cervix to the uterine lining and fallopian tubes. Despite the extent of the tissue involvement, a significant proportion of infections in both males (20-30%) and females (70%) result in no symptoms. Chlamydial infections can be transmitted both sexually and from mother to infant during the birth process. Because the focus of infection in the female is the cervix and endocervix rather than the vagina, female to male transmission is less efficient than male to female transmission. Immunity following infection is minimal and reinfection is common. However some immunity may develop with repeated infections. Chlamydia appears to cause one third to one half of all urethritis in men, 50-80% of mucupurulent cervicitis (ie, cervix with pus), and 10-40% of pelvic inflammatory disease. Though better data are needed, approximately 20% of women with chlamydial infections develop PID; 4% develop chronic pelvic pain; 3%, infertility; and 2%, adverse pregnancy outcomes (such as ectopic/tubal pregnancies).20

In one of the few studies to address the issue of whether oral sex poses a risk for chlamydial infection, throat cultures were performed on 706 male and 626 female STD patients. 3.7% of the men and 3.2% of the women had throat cultures positive for Chlamydia; women who practiced oral sex were three times as likely as those who did not to be culture positive (p = 0.01).21

CHANCROID, GRANULOMAINGUINALE , LYMPHOGRANULOMA VENEREUM, BACTERIAL VAGIN OSIS, AND TRICHOMONIASIS
There are a handful of case reports to suggest that chancroid –an ulcerative sexually transmitted disease common in developing countries – can be transmitted through oral sex. In contrast, there is little to no evidence to suggest that bacterial vaginosis, granuloma inguinale, lymphogranuloma venereum, or trichomoniasis can be transmitted through oral sex.2

CANDIDIASIS
Vulvovaginal candidiasis (yeast) infections were described in Greek writings and were linked to a fungal cause in the late 1800s.22 Most women (75%) have at least one yeast infection during their lifetime and about half of these have two or more.22

However not every woman with yeast in her genital (or gastrointestinal) tract is symptomatic; many women, particularly during pregnancy, may have candida without any symptoms. Natural immunity is cellular; antibodies offer no protection. Not unexpectedly, women with conditions that interfere with cellular immunity
such as diabetes, chemotherapy, or HIV infection – are at increased risk for recurrent vulvovaginal yeast infections. Although the vast majority of candidal infections are not sexually
transmitted, candida can be present in the male genital tract, and can contribute to recurrent infection in the female partner.23 24

There is some evidence that receptive oral sex in females increases the risk of vulvovaginal candidal infections, including recurrent infections. Female university students with culture-proven yeast infections were three and a half times as likely as their counterparts to have recently had receptive oral sex.25 In a cohort of women with repeated (ie, median 6) yeast infections, regular oral sex and recent oral sex were significantly associated with infection (odds ratio (OR) 2.4, 95% confidence interval (CI) 1.5 – 4.0 and OR 3.1, CI 1.5 – 6.8).26

HERPES 1 & 2
Herpes (Greek for “to creep”) infections have been recognized for more than 2,500 years. Although the infectious nature of the lesions was shown in the 1920s in both human and animal experiments, it wasn’t until the 1960s that German and American researchers parsed the virus into two types, herpes simplex 1

(HSV-1) and herpes simplex 2 (HSV-2).27 With the advent of laboratory tests, HSV-1 was shown to usually be associated with oral lesions (ie, cold sores), while HSV-2 was generally associated with genital lesions.28 However, HSV-2 can cause oral lesions and HSV-1 can cause genital lesions. Up to 50% of genital infections that are newly acquired late in pregnancy (ie, primary) cause herpes infection in the newborn; far fewer (ie, 4-5%) recurrent infections result in neonatal infection.29 Following primary infection (which may be either symptomatic or asymptomatic), both herpes viruses travel up nearby peripheral nerves to nerve roots located in the spinal cord, where they reside in a dormant state until temporarily reactivated.

Reactivation, like the initial infection, can be either symptomatic or asymptomatic (ie, lacking symptoms), and is accompanied by mucosal shedding of infectious viral particles. Most persons with newly acquired genital herpes will experience a recurrence (reactivation) during the year following initial infection; however, recurrences during the first year are more common with HSV-2 than with HSV-1 (90% vs. 60%).30 Transmission to a susceptible partner most commonly occurs during asymptomatic shedding.

Serosurveys (blood tests for evidence of past or current infection) suggest that HSV-1 is extremely common and varies by socioeconomic standing: 30-50% of middle-aged adults of high socioeconomic standing have evidence of infection with HSV-1 and 80-100% of persons with less wealth have evidence of infection.31 The proportion of adults infected with HSV-2 has changed dramatically over the last three decades: US visits for new genital infection increased 10-fold from 1970 to 1995 – from approximately 17,000 to 160,000 per 100,000 population.32

Evidence of infection also varies by sex and ethnicity, with females being more likely than males, and African Americans more likely than whites, to have evidence of infection. National serosurveys suggest that over 20% of the adult population in the US has evidence of HSV-2 infection.33

The practice of oral sex appears to be changing who has what type of herpes. Persons performing oral sex can transmit either HSV-1 or HSV-2 to susceptible (ie, nonimmune) partners if they are shedding virus. Conversely, persons performing oral sex may be exposed to either HSV-1 or HSV-2 if their partner is shedding and they are susceptible. New infections acquired in this manner may be either genital or oral/pharyngeal. Of STD clinic attendees in Seattle with positive HSV cultures, those who had experienced receptive oral sex during the preceding two months were 3 times more likely (OR 2.8, 95% CI 1.9-4.3) to have HSV-1 than HSV-2 infections.34 Similar findings were observed in persons presenting with first episodes of genital herpes in Sweden. Of HSV culture-positive persons who provided a history of sex practices, a history of oral sex was provided by 25/26 (96%) with HSV-1 and 8/14 (57%) with HSV-2.35 In some places, new HSV-1 genital infections now outnumber new HSV-2 infections. On one midwestern campus HSV-1 accounted for 29% of new genital herpes infections in 1993, but 78% in 2001.36 Of almost 500 persons belonging to a family practice who answered a questionnaire about sexual practices, the only significant predictor of HSV-2 infection in female minority patients was a history of oral sex.37 Throat infections with newly acquired herpes are common,38 are usually symptomatic, and can cause serious morbidity. A more than fourfold increase in the antibody titer (1:128 to 1:4096) to HSV-2 was observed in a patient hospitalized for pharyngitis of sufficient severity to threaten his airway; the patient gave a history of oral sex with a receptive female partner.39

HUMAN PAPILLOMA VIRUS
Of the more than 100 human papillomaviruses, approximately 35 cause human genital infections. However the clinical manifestations tend to vary by type. HPV 6 and 11 are usually associated with genital warts, and HPV 16, 18, 31, and 45 are typically associated with cancers of the genital tract (eg, cervix, anus).

Genital warts were described in the first century AD and attributed to a viral etiology in the early 1900s, but it wasn’t until the last few decades of the 20th century that the relationships between papillomaviruses and genital tract and anal cancers were confirmed.40

Microtrauma (tiny tears) during sex allows the virus to enter the skin or mucosa of the genital tract.41 Papillomavirus infections are exceedingly common and often (70%) go unrecognized. Current evidence suggests that more than half of sexually active adults are infected with one or more papillomaviruses.42 And a significant proportion of these are infected with HPV 16. In one nationally representative study (ie, NHANES) from the early 1990s, 13% of all persons in the US had antibodies (ie, evidence of past infection) against HPV 16 in their blood – 12.5% of whites, 19.1% of African Americans, and
8.9% of Hispanics.43 As the authors pointed out, since less than 60% of infected persons actually develop antibodies, this is an underestimate of the true proportion of infected persons. More recently, 21% (510/2,392) of 16- to 23-year-old females in university towns were excluded from an HPV vaccine trial because they had serologic evidence of prior HPV 16 infection.44 There is some suggestion that oral sex may be linked to adult onset respiratory papillomatosis (a condition most commonly associated with HPV 6 or 11 that manifests as hoarseness and is typically treated with a laser), asymptomatic oral papillomavirus, and oncogenic HPV strains of the cervix. Adults with recurrent respiratory papillomatosis (secondary to HPV) were significantly more likely than controls to practice oral sex.45 Almost all (99/101) patients with genital condyloma gave a history of practicing oral sex but none complained of oral symptoms. Oral papillomavirus was suspected by visual inspection in 8 and by culposcopy in 46; HPV DNA was identified in all 8 of the visually identified lesions and in 38 of the culposcopically identified lesions.46 Among Canadian university students presenting for routine Pap smears, women with 4 to 9 and 10 or more lifetime those with 0-3 lifetime oral sex partners to be infected with HPV
types associated with cancer (multivariate OR 2.4, CI 1.1 – 5.3 and OR 4.6, CI 1.3 –16.9, respectively).47

NONCHLAMYDIAL NONGONOCOCCAL URETHRITIS
Urethritis (urethral inflammation) is usually divided into gonococcal, chlamydial, and Chlamydia-negative nongonococcal urethritis (nonchlamydial NGU). Although white cells are usually present in the urine with urethritis, symptoms may be absent. Oral sex appears to be a risk factor for nonchlamydial NGU. In one study of men who have sex with men attending an STD clinic, 15.6% had nonchlamydial NGU. Men who practiced receptive (insertive) oral sex were twice as likely as other men to have nonchlamydial
NGU (multivariate OR 2.2, CI 1.3 – 3.7).48 Similar findings were observed for urethritis patients attending an STD clinic in Seville. Even after adjusting for homosexuality, men who practiced receptive (insertive) oral sex were almost 9 times (OR 8.8, CI 2.2-35.4) as likely as those who did not to have nonchlamydial (and
Ureaplasma-negative) NGU.49

H I V
In the early 1980s human immunodeficiency virus (HIV) was identified as the necessary but not causal agent underlying mysterious increases in Pneumocystis carinii pneumonia and Kaposi’s sarcoma in homosexual males. Two decades later, approximately 900,000 Americans have been infected with HIV and more than a half a million have died from acquired immunodeficiency syndrome (AIDS), the illness resulting from HIV infection.50 Authorities estimate that 20 million have died worldwide since the beginning of the epidemic and that 5 million are infected annually, 800,000 of them children.51 Three modes of transmission have been elucidated: bloodborne, sexual, and mother-to-child. From the late 1980s to the mid 1990s numerous case reports, published primarily as letters to the editor, suggested that HIV could be transmitted through oral sex. Rozenbaum and colleagues reported 5 homosexual men with new HIV infections whose only sexual activity was oral sex.52 Spitzer and Weiner reported a 60 year-old diabetic male with erectile dysfunction and new onset HIV infection. His only sexual contact besides his HIV (-) wife was a single prostitute whom he visited over a two-year period; only receptive and active oral sex was performed during these liaisons.53 Chin and Samarasinghe reported two homosexual men with new HIV cases. Both reported receptive oral intercourse with multiple partners but no anal intercourse without condoms. Both had histories of allergic sore throats.54 Additionally one study of hemophiliac couples was somewhat suggestive that oral sex was a possible route of transmission for HIV. In a study of 21 couples in which the hemophiliac male partner was HIV infected, 4 female partners were found to be HIV (+). Compared to couples in which the female partner remained HIV (-), couples in which both partners were HIV (+) were more likely to have engaged in oral sex (2/4 vs. 1/16 p 0.08).55

In 1996 an animal study showed that oral transmission of simian immunodeficiency virus (SIV), a virus closely related to HIV, was possible. In this study, a majority of monkeys were infected at a lower oral than rectal (nontraumatic) dose.56
Since then a number of studies have addressed HIV risk from oral sex; and a few have attempted to determine the proportion of new cases attributable to oral sex. Of 12 patients with newly acquired HIV infections who could specify sex practices in the month before illness, 4 recalled only oral sex. 3 of 4 practiced both active and receptive oral sex, and 1 only receptive oral sex.57 In a letter to the editor, Wallace and colleagues describe crack use and oral sex as risk factors for HIV acquisition in non-IV
drug-using female sex workers in New York. 21.5% of the workers who performed mostly oral sex were HIV (+) compared to 15% of those who performed mostly vaginal sex. Sex workers whose clients always used condoms when the worker performed oral sex were somewhat less likely than those whose clients used condoms inconsistently to be HIV (+) (14.7% vs. 25.4%).58 More than 2,000 high-risk, HIV (-) homosexual and bisexual men were followed over time during the early 1990s. The per-contact risk of receptive oral sex with an HIV (+) or HIV (unknown) partner was estimated to be 0.04% (4 per 10,000).59 Recent estimates of the proportion of new HIV cases attributable to oral sex range from less than 1%60 to 7%.61

SUMMARY
In summary, “oral sex” is sexual activity, and can serve as the route of transmission for a variety of sexually transmitted diseases. As such, it should not be considered or recommended as a substitute for penile-vaginal or penile-anal penetrative intercourse. A large proportion of adolescents and young adults who practice oral sex are also engaged in other sexual activities. Individuals, parents, educators, and policymakers need to be aware that any sexual activity with more than one monogamous, faithful, lifelong partner is associated with significant health risks.

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