Increase in oral sex and pharyngeal gonorrhoea: an unintended effect of a successful condom promotion programme for vaginal sex

Many countries have implemented successful condom promotion programmes, leading to a marked decline in sexually transmitted diseases (STD) and HIV[^1,2]. We observed a marked increase in oral sex, with a corresponding rise in pharyngeal gonorrhoea among female brothel-based sex workers in Singapore, after a successful condom promotion programme for vaginal sex.

All brothel-based sex workers in Singapore are required to undergo monthly screening for gonorrhoea and other STD. Data on sexual behaviour and condom use were collected from all of them in 1990 (n=808) and 1997 (n=806) and sampled cohorts for other years until 1998.

Cervical gonorrhoea declined markedly (Fig. 1) with increasing consistent condom use for vaginal sex, after a condom promotion programme for vaginal sex[³]. In contrast, the incidence of pharyngeal gonorrhoea rose from 0.37 per 100 person-months in 1992 to 1.32 per 100 person-months in 1996. The increase in pharyngeal gonorrhoea ran parallel to a marked increase in the practice of oral sex from 27.1% of sex workers in 1990 to 70.8% in 1996.

Fig. 1

Possible explanations for the rapid rise in oral sex are a change in sociodemographic characteristics of the sex workers over time, and a change in their sexual behaviour after a successful condom promotion programme for vaginal sex. There were significantly younger and more foreign sex workers in 1997 compared with 1990 (82.4% in the 20-29 years age group in 1997 versus 39.0% in 1990; foreign sex workers: 34.5% in 1997 versus 3.0% in 1990). The incidence of oral sex was 1.5 times higher among younger than older sex workers and 3.8 times higher among foreign or local Chinese sex workers than non-Chinese locals. The rapid increase in oral sex followed the increase in consistent condom use for vaginal sex (Fig. 1), suggesting that clients have demanded unprotected oral sex, often perceived to be safer, when pressured to use condoms for vaginal sex. This was confirmed subsequently by in-depth interviews with the sex workers. We also found that oral sex increased across all ages and ethnic groups and not only among younger, foreign or local Chinese sex workers. Although oral sex among local Chinese sex workers aged 20-29 years increased from 60.5% in 1990 to 95.5% in 1998, it also rose rapidly from 23.8 and 5.7% among the same ethnic group in the 30-39 and 40 years or older age groups to 88.1 and 50%, respectively, in 1998. Among the local non-Chinese sex workers, the prevalence of age-adjusted oral sex increased from 8.7% in 1990 to 30.5% in 1998.

Given the increasing evidence of HIV transmission by oral sex[^4-6], and infection with Neisseria gonorrhoeae [⁷] being a co-factor in HIV transmission, it is important to monitor oral sex and promote consistent condom use for this practice among sex workers. As demonstrated in our study, success in efforts to promote consistent condom use for vaginal sex may lead to an unintended effect such as a rise in oral sex with a corresponding increase in pharyngeal gonorrhoea. We implemented a condom promotion programme for oral sex after 1996, which led to increasing consistent condom use for oral sex and a concomitant decline in pharyngeal gonorrhoea to less than one episode per 100 person-months (Fig. 1).