Willard Cates

Sexually Transmitted Diseases Among American Youth: Incidence and Prevalence Estimates, 2000

CONTEXT In the United States, young people aged 15-24 represent 25% of the sexually experienced population. However, the incidence and prevalence of sexually transmitted diseases (STDs) among this age-group are unknown. METHODS Data from a variety of sources were used to estimate the incidence and prevalence of STDs among 15-24-year-olds in the United States in 2000. The quality and reliability of the estimates were categorized as good, fair or poor, depending on the quality of the data source. RESULTS Approximately 18.9 million new cases of STD occurred in 2000, of which 9.1 million (48%) were among persons aged 15-24. Three STDs (human papillomavirus, trichomoniasis and chlamydia) accounted for 88% of all new cases of STD among 15-24-year-olds. CONCLUSIONS These estimates emphasize the toll that STDs have on American youth. More representative data are needed to help monitor efforts at lowering the burden of these infections.

Sexual transmission of HIV

This article focuses on the epidemiology and biology of the host-related factors that affect the sexual transmission of HIV. It discusses host susceptibility and infectiousness environment biologic agent and preventing sexually transmitted HIV infection.

Genital chlamydial infections: epidemiology and reproductive sequelae.

Genital chlamydial infection is increasing and is now more common than gonorrhea. A sizable percentage of chlamydial infections of the lower genital tract in women progress to endometritis and salpingitis. Tubal infertility and ectopic pregnancy are important sequelae. Failure to control chlamydial infections reflects the following four factors: (1) Many cases are mild or asymptomatic; (2) diagnostic tests are expensive and technically demanding; (3) at least 7 days of multiple-dose therapy are currently required; and (4) partner notification is not routinely performed. Thus early identification of infected persons and compliance with curative therapy are less likely than with other sexually transmitted bacterial diseases.

ESTIMATES OF THE INCIDENCE AND PREVALENCE OF SEXUALLY TRANSMITTED DISEASESIN THE UNITED STATES

BACKGROUND Accurate, updated estimates of the incidence and prevalence of sexually transmitted infections in the United States remain elusive. The most widely quoted number of new sexually transmitted disease (STD) cases each year is 12 million. However, this figure has not changed in more than a decade, despite improvements in detection methods and the effects of STD control programs. GOALS To propose a system for weighing the strength of STD surveillance data and to estimate the incidence and prevalence of STDs in the United States for 1996, using the available published data. RESULTS We estimate that more than 15 million STD infections occurred in the United States in 1996. This number exceeds the earlier estimate primarily because improved detection techniques have allowed an assessment of previously undiagnosed infections. CONCLUSIONS Large numbers of new STDs continue to occur each year in the United States, with serious health and economic consequences. More than two thirds of our current estimate of 15 million STDs annually consists of two infections--trichomoniasis and human papillomavirus--for which we have only level III surveillance data. As the quality of our surveillance data improves, we can further refine the precision of our national estimates.

WORLDWIDE PATTERNS OF INFERTILITY: IS AFRICA DIFFERENT?

The World Health Organisation sponsored a multicentre, collaborative investigation of a standard approach to evaluating infertile couples. The study was conducted between 1979 and 1984 in thirty-three medical centres in twenty-five countries throughout the developed and developing world. Over 5800 couples completed the investigation. African centres had a pattern of infertility different from those in other developing regions or the developed countries. African couples were more likely than those from elsewhere to have secondary infertility or longer duration, a history of sexually transmitted diseases or pregnancy complications, and infertility diagnoses (such as bilateral tubal occlusion or pelvic adhesions) suggestive of previous genital infections.

Tenofovir Disoproxil Fumarate for Prevention of HIV Infection in Women: A Phase 2, Double- Blind, Randomized, Placebo-Controlled Trial

Objectives: The objective of this trial was to investigate the safety and preliminary effectiveness of a daily dose of 300 mg of tenofovir disoproxil fumarate (TDF) versus placebo in preventing HIV infection in women. Design: This was a phase 2, randomized, double-blind, placebo-controlled trial. Setting: The study was conducted between June 2004 and March 2006 in Tema, Ghana; Douala, Cameroon; and Ibadan, Nigeria. Participants: We enrolled 936 HIV-negative women at high risk of HIV infection into this study. Intervention: Participants were randomized 1:1 to once daily use of 300 mg of TDF or placebo. Outcome measures: The primary safety endpoints were grade 2 or higher serum creatinine elevations (>2.0 mg/dl) for renal function, grade 3 or 4 aspartate aminotransferase or alanine aminotransferase elevations (>170 U/l) for hepatic function, and grade 3 or 4 phosphorus abnormalities (<1.5 mg/dl). The effectiveness endpoint was infection with HIV-1 or HIV-2. Results: Study participants contributed 428 person-years of laboratory testing to the primary safety analysis. No significant differences emerged between treatment groups in clinical or laboratory safety outcomes. Study participants contributed 476 person-years of HIV testing to the primary effectiveness analysis, during which time eight seroconversions occurred. Two were diagnosed in participants randomized to TDF (0.86 per 100 person-years) and six in participants receiving placebo (2.48 per 100 person-years), yielding a rate ratio of 0.35 (95% confidence interval = 0.03–1.93), which did not achieve statistical significance. Owing to premature closures of the Cameroon and Nigeria study sites, the planned person-years of follow-up and study power could not be achieved. Conclusion: Daily oral use of TDF in HIV-uninfected women was not associated with increased clinical or laboratory adverse events. Effectiveness could not be conclusively evaluated because of the small number of HIV infections observed during the study.

Dual protection against unintended pregnancy and sexually transmitted infections: What is the best contraceptive approach?

In the midst of the global epidemics of both unintended pregnancy and sexually transmitted infection, contraceptive options that provide dual protection are ideal. However, those contraceptives with the best record of preventing pregnancy under typical use conditions (sterilization, hormonal methods, intrauterine devices) provide little if any protection against sexually transmitted infection. Alternatively, barrier contraceptive methods (specifically, condoms), which can reduce risks of many sexually transmitted infections, are associated with relatively higher pregnancy rates for most users than other contraceptives. This situation has produced a dilemma for those wishing to promote dual protection: whether to advocate use of two methods (one primarily to prevent pregnancy and the other primarily to prevent infections) or whether to emphasize use of condoms for both purposes. Data comparing these two approaches are limited and often contradictory. We discuss the underlying concepts of exposure to both pregnancy and infection, provide a broad overview of the effectiveness of contraceptive methods against these two conditions, present approaches to optimize dual protection, and propose several new directions for necessary research. In the absence of evidence-based recommendations, we believe clinicians should assist clients in assessing their likelihood of exposure to infection, either by prevalence of sexually transmitted infection in the community or by the specific risk factors of the client. If exposure is likely, particularly to the more serious infections such as human immunodeficiency virus, the one-method approach should be given greater weight. However, in settings where unintended pregnancy is the greater concern, emphasizing the two-methods approach as a first option may be appropriate.

The natural history of syphilis. Implications for the transmission dynamics and control of infection

Background: Syphilis remains a significant cause of morbidity in many developing countries and in some areas within North America and Europe. Mathematical models of the transmission dynamics of sexually transmitted infections have provided insights of relevance both to the interpretation of observed epidemiological patterns and to the design of control programs. Their use for the study of syphilis has been limited to date. Goals and Study Design: The authors investigated the trans‐mission dynamics of syphilis against a template based on the natural history of infection in individual patients with the aim of (1) identifying gaps in our understanding of the biology of infection, and (2) providing insights of relevance to the design of control policies. Results: Analyses reveal that Treponema pallidum has a moderate to high probability of transmission during contact between susceptible and infectious sexual partners. This, combined with questions over the existence of any immunity to reinfection, helps to ensure the long‐term persistence of syphilis within “core” activity groups. Patterns of treatment in North America are shown to have significantly altered the relative frequency of individuals in the different stages of disease. Conclusions: The analyses emphasize the benefits to be gained from treating infected people early in the primary stage of infection to reduce the effective period during which infected people can transmit to others. This form of treatment is beneficial for both the individual and the community. Treatment has greatly altered the incidence of different disease stages, but the full implications of treatment depend on whether immunity is present.

Contraception to prevent HIV-positive births: current contribution and potential cost savings in PEPFAR countries

Objectives: To estimate the number of HIV-positive births currently prevented by contraceptive use in the President’s Emergency Plan for AIDS Relief (PEPFAR) focus countries and to estimate the first year cost savings to each country if unintended and unwanted HIV-positive births were prevented via contraceptive use rather than providing antiretroviral prophylaxis for HIV-positive pregnant women (“PMTCT services”). Methods: Data from publicly available sources yielded estimates of (1) contraceptive and HIV prevalence; (2) the number of women of reproductive age; (3) the number of annual births to HIV-infected women; (4) the rates of pregnancy and vertical HIV transmission; (5) the proportions of unintended and unwanted births; and (6) the cost per HIV-positive birth averted by family planning and PMTCT services. The number of HIV-positive births currently averted by contraceptive use and the number of unwanted and unintended HIV-positive births are the product of these estimates. Cost savings are the difference in the costs of family planning and PMTCT services. Results: The annual number of unintended HIV-positive births currently averted by contraceptive use ranges from 178 in Guyana to over 120 000 in South Africa. The minimum annual cost savings to prevent just the unwanted HIV-positive births ranges from

The time has come for common ground on preventing sexual transmission of HIV.

26 000 in Vietnam to over