Portal de Periódicos da CAPES

Global epidemiology of sexually transmitted diseases

1998; Elsevier BV; Volume: 351; Linguagem: Inglês

10.1016/s0140-6736(98)90001-0

1474-547X

Antonio Gerbase, Jane Rowley, T. Mertens,

Adolescent Sexual and Reproductive Health

Sexually transmitted diseases (STDs), or sexually transmitted infections (STIs), have been recognised as a major public-health problem for a number of years. In 1912, Prince Morrow, chair of the US committee looking into the problem of venereal diseases, was quoted as saying "It is a conservative estimate that fully one-eighth of all human suffering comes from this source".1Brandt AM No magic bullet. Oxford University Press, Oxford1987Google Scholar Despite medical advances, STDs continue to pose a threat to the health and welfare of individuals.In the last decade there have been considerable advances in the field of STDs. These have been fuelled to a large extent by the HIV/AIDS epidemic, but also by increased recognition of the range and severity of complications and sequelae that can be linked to these infections and the development of new case-management approaches. More than 30 bacterial, viral, and parasitic diseases have now been identified that can be transmitted by the sexual route; only a minority have sexual transmission as their dominant route of spread, however. For example, in areas with low hygiene standards or poor living conditions, hepatitis B and cytomegalovirus are often acquired through non-sexual routes in childhood.STDs infect the reproductive tract as their primary site, with transmission occurring during sexual intercourse or from mother to child during pregnancy and childbirth. As a result, the greatest risk of infection is found among sexually active individuals and in infants born to infected mothers. Multiple infections within the same individual are also frequent,2Behets FMT Desormeaux J Joseph D et al.Control of sexually transmitted diseases in Haiti: results and implications of a baseline study among pregnant women living in Cite Soleil shantytowns.J Infect Dis. 1995; 172: 764-771Crossref PubMed Scopus (58) Google Scholar as is reinfection if partners have not been adequately treated.Incidence and prevalence of STDsThe two main sources of information on the prevalence and incidence of a particular disease are case-notification reports and epidemiological studies. In countries with good reporting systems, the number of reported cases is a good proxy for the total number of infections if the disease has very definite symptoms. STDs, however, are often symptomless and when there are symptoms they are often not specific. For example, estimates indicate that 70–75% of women infected with Chlamydia trachomatis are symptom-free. In addition, the social stigma associated with an STD may result in people seeking care from alternative providers or not seeking any care. As a result, report-based STD surveillance systems tend to underestimate substantially the total number of new cases.In 1996, WHO generated a new set of global estimates for four major STDs drawing on an extensive review of the published and unpublished prevalence data.3WHO/Global Program on AIDS Global prevalence and incidences of selected curable sexually transmitted diseases: overview and estimates.WHO/GPA/STD. 1995; 1: 1-26Google Scholar, 4Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google Scholar These estimates suggest that there were more than 333 million new cases of syphilis, gonorrhoea, chlamydia, and trichomoniasis in adults aged 1549 years in 1995: 12·2 million cases of syphilis, 62·2 million cases of gonorrhoea, 89·1 million of chlamydia, and 167·2 million of trichomoniasis (panel). Geographically, the vast majority of these new cases occurred in the developing world, which reflects the global distribution of population. The largest number of new infections occurred in the region of south and southeast Asia (45·6%), followed by sub-Saharan Africa (19·7%), and then Latin America and the Caribbean (10·9%; figure 1). It should be noted, however, that these four infections account for only a proportion of infections acquired through sexual intercourse each year.PanelEstimated incidence of STDs (millions) in people aged 15-49 years for 19954Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google ScholarTabled 1SyphilisGonorrhoeaChlamydiaTrichomoniasisMenWomenMenWomenMenWomenMenWomenNorth America0·0720·0720·830·921·642·343·784·23Western Europe0·100·100·600·632·303·205·305·76Australasia0·0050·0050·6630·0690·120·170·290·32Latin America and the Caribbean0·560·703·453·675·015·128·529·10Sub-Saharan Africa1·561·977·4308·386·968·415·0715·35North Africa and Middle East6·280·330·770·771·671·282·322·22Eastern Europe and central: Asia0·050.0·0501·17.1·162·152·924·95·17East Asia and Pacific0·260·301·801·472·702·634·834·53South and southeast Asia2·663·1314·5614·5520·220·2839·5635·87Total5·556·6630·5431·6242·7546·3884·6082·55 Open table in a new tab The WHO estimates, although based on a comprehensive survey of the available information,4Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google Scholar are limited by the quantity and quality of prevalence data available from the different regions and our knowledge of the duration of infection. Interpreting the data from prevalence studies and comparing results is further complicated by: the nature of the populations studied (the majority of data originate from studies carried out in "convenient" populations, such as STD or antenatal clinic attendees), small sample sizes, and the different diagnostic approaches used.Data from epidemiological surveys show that within countries and between countries in the same region, the prevalence and incidence of STDs may vary widely even in similar population groups. These differences reflect a variety of social, cultural, and economic factors, as illustrated by the HIV epidemic, and also access to appropriate treatment (figure 2).5Wasserheit J The significance and scope of reproductive tract infections among Third World women.Suppl Int J Gynecol Obstet. 1989; 3: 145-168Summary Full Text PDF PubMed Scopus (116) Google Scholar, 6Mertens TE Piot P Global aspects of human immunodeficiency virus epidemiology: general considerations.in: De Vita Jr, V Hellman S Rosenberg SA AIDS: biology, diagnosis, treatment and prevention. 4th ed. Lippincott-Raven, Philadelphia1997Google Scholar In general, the prevalence of STDs tends to be higher in urban residents, in unmarried individuals, and in young adults. STDs tend to occur at a younger age in females than in males, related to patterns of sexual activity and to the relative rates of transmission from one sex to the other.Figure 2Selected factors associated with female reproductive-tract infections (RTIs) in developing countries5Wasserheit J The significance and scope of reproductive tract infections among Third World women.Suppl Int J Gynecol Obstet. 1989; 3: 145-168Summary Full Text PDF PubMed Scopus (116) Google ScholarShow full captionReprinted from ref 5i copyright 1989, with permission from Elsevier ScienceView Large Image Figure ViewerDownload Hi-res image Download (PPT)At the population level, the spread of an STD depends upon the average number of new cases of infection generated by an infected person. This can be described in terms of the basic or case-reproduction ratio (Ro) which, for an STD, depends upon the efficiency of transmission (β), the mean rate of sexual partner change (c), and the average duration of infectiousness (D).7Anderson RM May RM Infectious diseases of humans: dynamics and control. Oxford University Press, 1992Google Scholar The higher the value of Ro the greater the potential for the spread of the infection: Ro=βcDFurthermore, the ways in which infected persons seek care, and the consequent delays in diagnosis and treatment, influence STD incidence and the probability of complications.8Ward H Mertens TE Thomas C Health seeking behaviour and the control of sexually transmitted disease.Health Policy Planning. 1997; 12: 19-28Crossref PubMed Scopus (71) Google Scholar Data on this issue are scarce, and better understanding of health-seeking behaviour is necessary to design STD interventions.Disease burdenIn the 1993 World Development Report,9World Development Report 1993. Oxford University Press, Oxford1993Google Scholar 1990 estimates suggested that, in demographically developing countries, STDs excluding HIV accounted for 8·9% of the disease burden in women aged 15–45 years and 1·5% in men in the same age class. This ranked STDs, excluding HIV, as the second major cause of lost disability-adjusted life years in women of reproductive age.The vast majority of the disease burden from STDs is a result of the complications and sequelae that may follow infection. For example, primary infection with gonorrhoea and chlamydia in women is usually symptomless. When left untreated, however, infections may migrate upwards from the lower reproductive tract and lead to pelvic inflammatory disease (inflammation of the uterus, fallopian tubes, ovarian, or other pelvic structures), chronic pelvic pain, tubo-ovarian abscesses, ectopic pregnancies, and infertility. In addition, untreated infections in pregnant women may result in fetal loss, stillbirths, low birth weight, and eye and lung damage in the newborn. Unraveling the relations between infection and the frequency and severity of its consequences is a complex exercise10Rowley J Berkley S Sexually transmitted diseases.in: Murray CJL Lopez AD Health dimensions of sex and reproduction: the global burden of sexually transmitted diseases, HIV, maternal conditions, perinatal disorders, and congenital anomalies. Harvard University Press, Cambridge1998Google Scholar and few data are available; most studies have focused on assessing the aetiology of particular complications rather than the probability of developing a particular complication following infection.STD prevention and careThe control of STDs is a public-health priority and one that has become of even higher priority with the HIV epidemic. Since STDs and HIV share many behavioural risk factors, efforts to encourage individuals to modify sexual behaviours and adopt safer sexual practices will have a beneficial impact on both. In addition, data from a number of studies strongly suggest that both ulcerative and non-ulcerative STDs facilitate HIV transmission.11Laga M Manoka A Kivuvu M et al.Non-ulcerative sexually transmitted diseases as risk factors for HIV-1 transmission in women: results from a cohort study.AIDS. 1993; 7: 95-102Crossref PubMed Scopus (1029) Google Scholar As a result, a community-based, randomised trial has been proposed to examine whether strengthening STD control and, in particular, the treatment of STDs, could be an important way to reduce the transmission of HIV.12Mertens TE Hayes RJ Smith PG Epidemiological methods to study the interaction of HIV infection and other sexually transmitted diseases.AIDS. 1990; 4: 57-65Crossref PubMed Scopus (110) Google Scholar Results from such a study in the Mwanza Region, Tanzania, have shown that this is indeed the case. A 42% reduction in the incidence of HIV was documented in the intervention communities that received improved STD treatment at a cost of US$10·15 per STD case treated.13Grosskurth H Mosha F Todd J et al.Impact of improved treatment of STD on HIV infection in rural Tanzania: randomised controlled trial.Lancet. 1995; 346: 530-536PubMed Scopus (1177) Google Scholar, 14Gilson L Mkanje R Grosskurth H et al.Cost-effectiveness of improved treatment services for sexually transmitted diseases in preventing HIV-1 infection in Mwanza Region, Tanzania.Lancet. 1997; 350: 1805-1809Summary Full Text Full Text PDF PubMed Scopus (142) Google ScholarEnsuring prompt and effective treatment for all individuals with symptomatic infections is a challenge for health-care providers, especially with the development of antimicrobial resistance. Already, resistance in Neisseria gonorrhoeae is problematic and is emerging in Haemophilus ducreyi (see p s8). Ensuring prompt and effective treatment for symptom-free individuals, however, is an even bigger challenge and will require the development of new diagnostic tools that not only can detect symptomless infections but are rapid, non-invasive, easy to use, and inexpensive.Even with improved STD treatment and prevention activities, individuals will remain whose initial infections were not diagnosed or treated appropriately. As a result, improving the diagnosis and clinical care of their complications and sequelae should be part of any comprehensive STD programme.Evidence based on trends in reported cases suggests that public-health programmes have been effective in reducing the incidence of STDs. However, such trends need to be interpreted with caution, because differences in reported cases may reflect changes in how data were collected and access to care rather than a change in incidence. Despite this caveat, the data suggest grounds for optimism. For example, in Norway, the number of reported cases of gonorrhoea fell from more than 10 000 in 1981 to less than 300 in 1993.15National Institute of Public Health (Norway) MSIS report. NIPH, Oslo1993Google Scholar In Costa Rica, Chile, Zimbabwe, and Thailand, steady and sustained declines in reported STD cases have also been documented following active prevention programmes.16PAHO/WHO AIDS, HIV & STD annual surveillance report for the Americas. 1992Google Scholar, 17Ministry of Health and Child Welfare (Zimbabwe) National AIDS Coordination Programme Annual Report. MHCW, Harare1995Google Scholar, 18Hanenberg RS Rojanapithayakorn W Kunasol P Sokal DC Impact of Thailand's HIV-control programme as indicated by the decline of sexually transmitted diseases.Lancet. 1994; 344: 243-245Summary PubMed Scopus (374) Google Scholar Reduction of the prevalence and burden of disease associated with STDs requires a concerted effort by national public-health services, international and bilateral agencies, nongovernmental organisations, the private sector, and research institutions. A comprehensive, multifaceted strategy is required, which can address a problem that originates in the complex web of social and biological systems.Primary and secondary prevention programmes need to be strengthened and integrated into health systems, and must be accessible to all. Key elements of these programmes include: first, health-promotion approaches aimed at empowering individuals and communities to avoid situations of risk in their specific social context; second, improved access to and quality of STD services including screening for curable STDs; third, improved access to technologies that people can use to prevent infection (eg, condoms); fourth, reduction of the stigma associated with STDs;19WHO/UNAIDS Sexually transmitted diseases: policies and principles for prevention and care. WHO, Geneva1997Google Scholar and, finally, improved surveillance.More research will also be required to improve this process, mainly directed at increasing our knowledge of the distribution of these infections, the link between infection and the development of different complications, and the role played by different factors (eg, genetic, environmental, and cultural) in the development of complications. Sexually transmitted diseases (STDs), or sexually transmitted infections (STIs), have been recognised as a major public-health problem for a number of years. In 1912, Prince Morrow, chair of the US committee looking into the problem of venereal diseases, was quoted as saying "It is a conservative estimate that fully one-eighth of all human suffering comes from this source".1Brandt AM No magic bullet. Oxford University Press, Oxford1987Google Scholar Despite medical advances, STDs continue to pose a threat to the health and welfare of individuals. In the last decade there have been considerable advances in the field of STDs. These have been fuelled to a large extent by the HIV/AIDS epidemic, but also by increased recognition of the range and severity of complications and sequelae that can be linked to these infections and the development of new case-management approaches. More than 30 bacterial, viral, and parasitic diseases have now been identified that can be transmitted by the sexual route; only a minority have sexual transmission as their dominant route of spread, however. For example, in areas with low hygiene standards or poor living conditions, hepatitis B and cytomegalovirus are often acquired through non-sexual routes in childhood. STDs infect the reproductive tract as their primary site, with transmission occurring during sexual intercourse or from mother to child during pregnancy and childbirth. As a result, the greatest risk of infection is found among sexually active individuals and in infants born to infected mothers. Multiple infections within the same individual are also frequent,2Behets FMT Desormeaux J Joseph D et al.Control of sexually transmitted diseases in Haiti: results and implications of a baseline study among pregnant women living in Cite Soleil shantytowns.J Infect Dis. 1995; 172: 764-771Crossref PubMed Scopus (58) Google Scholar as is reinfection if partners have not been adequately treated. Incidence and prevalence of STDsThe two main sources of information on the prevalence and incidence of a particular disease are case-notification reports and epidemiological studies. In countries with good reporting systems, the number of reported cases is a good proxy for the total number of infections if the disease has very definite symptoms. STDs, however, are often symptomless and when there are symptoms they are often not specific. For example, estimates indicate that 70–75% of women infected with Chlamydia trachomatis are symptom-free. In addition, the social stigma associated with an STD may result in people seeking care from alternative providers or not seeking any care. As a result, report-based STD surveillance systems tend to underestimate substantially the total number of new cases.In 1996, WHO generated a new set of global estimates for four major STDs drawing on an extensive review of the published and unpublished prevalence data.3WHO/Global Program on AIDS Global prevalence and incidences of selected curable sexually transmitted diseases: overview and estimates.WHO/GPA/STD. 1995; 1: 1-26Google Scholar, 4Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google Scholar These estimates suggest that there were more than 333 million new cases of syphilis, gonorrhoea, chlamydia, and trichomoniasis in adults aged 1549 years in 1995: 12·2 million cases of syphilis, 62·2 million cases of gonorrhoea, 89·1 million of chlamydia, and 167·2 million of trichomoniasis (panel). Geographically, the vast majority of these new cases occurred in the developing world, which reflects the global distribution of population. The largest number of new infections occurred in the region of south and southeast Asia (45·6%), followed by sub-Saharan Africa (19·7%), and then Latin America and the Caribbean (10·9%; figure 1). It should be noted, however, that these four infections account for only a proportion of infections acquired through sexual intercourse each year.PanelEstimated incidence of STDs (millions) in people aged 15-49 years for 19954Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google ScholarTabled 1SyphilisGonorrhoeaChlamydiaTrichomoniasisMenWomenMenWomenMenWomenMenWomenNorth America0·0720·0720·830·921·642·343·784·23Western Europe0·100·100·600·632·303·205·305·76Australasia0·0050·0050·6630·0690·120·170·290·32Latin America and the Caribbean0·560·703·453·675·015·128·529·10Sub-Saharan Africa1·561·977·4308·386·968·415·0715·35North Africa and Middle East6·280·330·770·771·671·282·322·22Eastern Europe and central: Asia0·050.0·0501·17.1·162·152·924·95·17East Asia and Pacific0·260·301·801·472·702·634·834·53South and southeast Asia2·663·1314·5614·5520·220·2839·5635·87Total5·556·6630·5431·6242·7546·3884·6082·55 Open table in a new tab The WHO estimates, although based on a comprehensive survey of the available information,4Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google Scholar are limited by the quantity and quality of prevalence data available from the different regions and our knowledge of the duration of infection. Interpreting the data from prevalence studies and comparing results is further complicated by: the nature of the populations studied (the majority of data originate from studies carried out in "convenient" populations, such as STD or antenatal clinic attendees), small sample sizes, and the different diagnostic approaches used.Data from epidemiological surveys show that within countries and between countries in the same region, the prevalence and incidence of STDs may vary widely even in similar population groups. These differences reflect a variety of social, cultural, and economic factors, as illustrated by the HIV epidemic, and also access to appropriate treatment (figure 2).5Wasserheit J The significance and scope of reproductive tract infections among Third World women.Suppl Int J Gynecol Obstet. 1989; 3: 145-168Summary Full Text PDF PubMed Scopus (116) Google Scholar, 6Mertens TE Piot P Global aspects of human immunodeficiency virus epidemiology: general considerations.in: De Vita Jr, V Hellman S Rosenberg SA AIDS: biology, diagnosis, treatment and prevention. 4th ed. Lippincott-Raven, Philadelphia1997Google Scholar In general, the prevalence of STDs tends to be higher in urban residents, in unmarried individuals, and in young adults. STDs tend to occur at a younger age in females than in males, related to patterns of sexual activity and to the relative rates of transmission from one sex to the other.At the population level, the spread of an STD depends upon the average number of new cases of infection generated by an infected person. This can be described in terms of the basic or case-reproduction ratio (Ro) which, for an STD, depends upon the efficiency of transmission (β), the mean rate of sexual partner change (c), and the average duration of infectiousness (D).7Anderson RM May RM Infectious diseases of humans: dynamics and control. Oxford University Press, 1992Google Scholar The higher the value of Ro the greater the potential for the spread of the infection: Ro=βcDFurthermore, the ways in which infected persons seek care, and the consequent delays in diagnosis and treatment, influence STD incidence and the probability of complications.8Ward H Mertens TE Thomas C Health seeking behaviour and the control of sexually transmitted disease.Health Policy Planning. 1997; 12: 19-28Crossref PubMed Scopus (71) Google Scholar Data on this issue are scarce, and better understanding of health-seeking behaviour is necessary to design STD interventions. The two main sources of information on the prevalence and incidence of a particular disease are case-notification reports and epidemiological studies. In countries with good reporting systems, the number of reported cases is a good proxy for the total number of infections if the disease has very definite symptoms. STDs, however, are often symptomless and when there are symptoms they are often not specific. For example, estimates indicate that 70–75% of women infected with Chlamydia trachomatis are symptom-free. In addition, the social stigma associated with an STD may result in people seeking care from alternative providers or not seeking any care. As a result, report-based STD surveillance systems tend to underestimate substantially the total number of new cases. In 1996, WHO generated a new set of global estimates for four major STDs drawing on an extensive review of the published and unpublished prevalence data.3WHO/Global Program on AIDS Global prevalence and incidences of selected curable sexually transmitted diseases: overview and estimates.WHO/GPA/STD. 1995; 1: 1-26Google Scholar, 4Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google Scholar These estimates suggest that there were more than 333 million new cases of syphilis, gonorrhoea, chlamydia, and trichomoniasis in adults aged 1549 years in 1995: 12·2 million cases of syphilis, 62·2 million cases of gonorrhoea, 89·1 million of chlamydia, and 167·2 million of trichomoniasis (panel). Geographically, the vast majority of these new cases occurred in the developing world, which reflects the global distribution of population. The largest number of new infections occurred in the region of south and southeast Asia (45·6%), followed by sub-Saharan Africa (19·7%), and then Latin America and the Caribbean (10·9%; figure 1). It should be noted, however, that these four infections account for only a proportion of infections acquired through sexual intercourse each year. Tabled 1SyphilisGonorrhoeaChlamydiaTrichomoniasisMenWomenMenWomenMenWomenMenWomenNorth America0·0720·0720·830·921·642·343·784·23Western Europe0·100·100·600·632·303·205·305·76Australasia0·0050·0050·6630·0690·120·170·290·32Latin America and the Caribbean0·560·703·453·675·015·128·529·10Sub-Saharan Africa1·561·977·4308·386·968·415·0715·35North Africa and Middle East6·280·330·770·771·671·282·322·22Eastern Europe and central: Asia0·050.0·0501·17.1·162·152·924·95·17East Asia and Pacific0·260·301·801·472·702·634·834·53South and southeast Asia2·663·1314·5614·5520·220·2839·5635·87Total5·556·6630·5431·6242·7546·3884·6082·55 Open table in a new tab The WHO estimates, although based on a comprehensive survey of the available information,4Gerbase AC Rowley JT Heymann DHL et al.Global prevalence and incidence estimates of selected curable STDs.Genitourin Med. 1998; (in press)Google Scholar are limited by the quantity and quality of prevalence data available from the different regions and our knowledge of the duration of infection. Interpreting the data from prevalence studies and comparing results is further complicated by: the nature of the populations studied (the majority of data originate from studies carried out in "convenient" populations, such as STD or antenatal clinic attendees), small sample sizes, and the different diagnostic approaches used. Data from epidemiological surveys show that within countries and between countries in the same region, the prevalence and incidence of STDs may vary widely even in similar population groups. These differences reflect a variety of social, cultural, and economic factors, as illustrated by the HIV epidemic, and also access to appropriate treatment (figure 2).5Wasserheit J The significance and scope of reproductive tract infections among Third World women.Suppl Int J Gynecol Obstet. 1989; 3: 145-168Summary Full Text PDF PubMed Scopus (116) Google Scholar, 6Mertens TE Piot P Global aspects of human immunodeficiency virus epidemiology: general considerations.in: De Vita Jr, V Hellman S Rosenberg SA AIDS: biology, diagnosis, treatment and prevention. 4th ed. Lippincott-Raven, Philadelphia1997Google Scholar In general, the prevalence of STDs tends to be higher in urban residents, in unmarried individuals, and in young adults. STDs tend to occur at a younger age in females than in males, related to patterns of sexual activity and to the relative rates of transmission from one sex to the other. At the population level, the spread of an STD depends upon the average number of new cases of infection generated by an infected person. This can be described in terms of the basic or case-reproduction ratio (Ro) which, for an STD, depends upon the efficiency of transmission (β), the mean rate of sexual partner change (c), and the average duration of infectiousness (D).7Anderson RM May RM Infectious diseases of humans: dynamics and control. Oxford University Press, 1992Google Scholar The higher the value of Ro the greater the potential for the spread of the infection: Ro=βcD Furthermore, the ways in which infected persons seek care, and the consequent delays in diagnosis and treatment, influence STD incidence and the probability of complications.8Ward H Mertens TE Thomas C Health seeking behaviour and the control of sexually transmitted disease.Health Policy Planning. 1997; 12: 19-28Crossref PubMed Scopus (71) Google Scholar Data on this issue are scarce, and better understanding of health-seeking behaviour is necessary to design STD interventions. Disease burdenIn the 1993 World Development Report,9World Development Report 1993. Oxford University Press, Oxford1993Google Scholar 1990 estimates suggested that, in demographically developing countries, STDs excluding HIV accounted for 8·9% of the disease burden in women aged 15–45 years and 1·5% in men in the same age class. This ranked STDs, excluding HIV, as the second major cause of lost disability-adjusted life years in women of reproductive age.The vast majority of the disease burden from STDs is a result of the complications and sequelae that may follow infection. For example, primary infection with gonorrhoea and chlamydia in women is usually symptomless. When left untreated, however, infections may migrate upwards from the lower reproductive tract and lead to pelvic inflammatory disease (inflammation of the uterus, fallopian tubes, ovarian, or other pelvic structures), chronic pelvic pain, tubo-ovarian abscesses, ectopic pregnancies, and infertility. In addition, untreated infections in pregnant women may result in fetal loss, stillbirths, low birth weight, and eye and lung damage in the newborn. Unraveling the relations between infection and the frequency and severity of its consequences is a complex exercise10Rowley J Berkley S Sexually transmitted diseases.in: Murray CJL Lopez AD Health dimensions of sex and reproduction: the global burden of sexually transmitted diseases, HIV, maternal conditions, perinatal disorders, and congenital anomalies. Harvard University Press, Cambridge1998Google Scholar and few data are available; most studies have focused on assessing the aetiology of particular complications rather than the probability of developing a particular complication following infection. In the 1993 World Development Report,9World Development Report 1993. Oxford University Press, Oxford1993Google Scholar 1990 estimates suggested that, in demographically developing countries, STDs excluding HIV accounted for 8·9% of the disease burden in women aged 15–45 years and 1·5% in men in the same age class. This ranked STDs, excluding HIV, as the second major cause of lost disability-adjusted life years in women of reproductive age. The vast majority of the disease burden from STDs is a result of the complications and sequelae that may follow infection. For example, primary infection with gonorrhoea and chlamydia in women is usually symptomless. When left untreated, however, infections may migrate upwards from the lower reproductive tract and lead to pelvic inflammatory disease (inflammation of the uterus, fallopian tubes, ovarian, or other pelvic structures), chronic pelvic pain, tubo-ovarian abscesses, ectopic pregnancies, and infertility. In addition, untreated infections in pregnant women may result in fetal loss, stillbirths, low birth weight, and eye and lung damage in the newborn. Unraveling the relations between infection and the frequency and severity of its consequences is a complex exercise10Rowley J Berkley S Sexually transmitted diseases.in: Murray CJL Lopez AD Health dimensions of sex and reproduction: the global burden of sexually transmitted diseases, HIV, maternal conditions, perinatal disorders, and congenital anomalies. Harvard University Press, Cambridge1998Google Scholar and few data are available; most studies have focused on assessing the aetiology of particular complications rather than the probability of developing a particular complication following infection. STD prevention and careThe control of STDs is a public-health priority and one that has become of even higher priority with the HIV epidemic. Since STDs and HIV share many behavioural risk factors, efforts to encourage individuals to modify sexual behaviours and adopt safer sexual practices will have a beneficial impact on both. In addition, data from a number of studies strongly suggest that both ulcerative and non-ulcerative STDs facilitate HIV transmission.11Laga M Manoka A Kivuvu M et al.Non-ulcerative sexually transmitted diseases as risk factors for HIV-1 transmission in women: results from a cohort study.AIDS. 1993; 7: 95-102Crossref PubMed Scopus (1029) Google Scholar As a result, a community-based, randomised trial has been proposed to examine whether strengthening STD control and, in particular, the treatment of STDs, could be an important way to reduce the transmission of HIV.12Mertens TE Hayes RJ Smith PG Epidemiological methods to study the interaction of HIV infection and other sexually transmitted diseases.AIDS. 1990; 4: 57-65Crossref PubMed Scopus (110) Google Scholar Results from such a study in the Mwanza Region, Tanzania, have shown that this is indeed the case. A 42% reduction in the incidence of HIV was documented in the intervention communities that received improved STD treatment at a cost of US$10·15 per STD case treated.13Grosskurth H Mosha F Todd J et al.Impact of improved treatment of STD on HIV infection in rural Tanzania: randomised controlled trial.Lancet. 1995; 346: 530-536PubMed Scopus (1177) Google Scholar, 14Gilson L Mkanje R Grosskurth H et al.Cost-effectiveness of improved treatment services for sexually transmitted diseases in preventing HIV-1 infection in Mwanza Region, Tanzania.Lancet. 1997; 350: 1805-1809Summary Full Text Full Text PDF PubMed Scopus (142) Google ScholarEnsuring prompt and effective treatment for all individuals with symptomatic infections is a challenge for health-care providers, especially with the development of antimicrobial resistance. Already, resistance in Neisseria gonorrhoeae is problematic and is emerging in Haemophilus ducreyi (see p s8). Ensuring prompt and effective treatment for symptom-free individuals, however, is an even bigger challenge and will require the development of new diagnostic tools that not only can detect symptomless infections but are rapid, non-invasive, easy to use, and inexpensive.Even with improved STD treatment and prevention activities, individuals will remain whose initial infections were not diagnosed or treated appropriately. As a result, improving the diagnosis and clinical care of their complications and sequelae should be part of any comprehensive STD programme.Evidence based on trends in reported cases suggests that public-health programmes have been effective in reducing the incidence of STDs. However, such trends need to be interpreted with caution, because differences in reported cases may reflect changes in how data were collected and access to care rather than a change in incidence. Despite this caveat, the data suggest grounds for optimism. For example, in Norway, the number of reported cases of gonorrhoea fell from more than 10 000 in 1981 to less than 300 in 1993.15National Institute of Public Health (Norway) MSIS report. NIPH, Oslo1993Google Scholar In Costa Rica, Chile, Zimbabwe, and Thailand, steady and sustained declines in reported STD cases have also been documented following active prevention programmes.16PAHO/WHO AIDS, HIV & STD annual surveillance report for the Americas. 1992Google Scholar, 17Ministry of Health and Child Welfare (Zimbabwe) National AIDS Coordination Programme Annual Report. MHCW, Harare1995Google Scholar, 18Hanenberg RS Rojanapithayakorn W Kunasol P Sokal DC Impact of Thailand's HIV-control programme as indicated by the decline of sexually transmitted diseases.Lancet. 1994; 344: 243-245Summary PubMed Scopus (374) Google Scholar Reduction of the prevalence and burden of disease associated with STDs requires a concerted effort by national public-health services, international and bilateral agencies, nongovernmental organisations, the private sector, and research institutions. A comprehensive, multifaceted strategy is required, which can address a problem that originates in the complex web of social and biological systems.Primary and secondary prevention programmes need to be strengthened and integrated into health systems, and must be accessible to all. Key elements of these programmes include: first, health-promotion approaches aimed at empowering individuals and communities to avoid situations of risk in their specific social context; second, improved access to and quality of STD services including screening for curable STDs; third, improved access to technologies that people can use to prevent infection (eg, condoms); fourth, reduction of the stigma associated with STDs;19WHO/UNAIDS Sexually transmitted diseases: policies and principles for prevention and care. WHO, Geneva1997Google Scholar and, finally, improved surveillance.More research will also be required to improve this process, mainly directed at increasing our knowledge of the distribution of these infections, the link between infection and the development of different complications, and the role played by different factors (eg, genetic, environmental, and cultural) in the development of complications. The control of STDs is a public-health priority and one that has become of even higher priority with the HIV epidemic. Since STDs and HIV share many behavioural risk factors, efforts to encourage individuals to modify sexual behaviours and adopt safer sexual practices will have a beneficial impact on both. In addition, data from a number of studies strongly suggest that both ulcerative and non-ulcerative STDs facilitate HIV transmission.11Laga M Manoka A Kivuvu M et al.Non-ulcerative sexually transmitted diseases as risk factors for HIV-1 transmission in women: results from a cohort study.AIDS. 1993; 7: 95-102Crossref PubMed Scopus (1029) Google Scholar As a result, a community-based, randomised trial has been proposed to examine whether strengthening STD control and, in particular, the treatment of STDs, could be an important way to reduce the transmission of HIV.12Mertens TE Hayes RJ Smith PG Epidemiological methods to study the interaction of HIV infection and other sexually transmitted diseases.AIDS. 1990; 4: 57-65Crossref PubMed Scopus (110) Google Scholar Results from such a study in the Mwanza Region, Tanzania, have shown that this is indeed the case. A 42% reduction in the incidence of HIV was documented in the intervention communities that received improved STD treatment at a cost of US$10·15 per STD case treated.13Grosskurth H Mosha F Todd J et al.Impact of improved treatment of STD on HIV infection in rural Tanzania: randomised controlled trial.Lancet. 1995; 346: 530-536PubMed Scopus (1177) Google Scholar, 14Gilson L Mkanje R Grosskurth H et al.Cost-effectiveness of improved treatment services for sexually transmitted diseases in preventing HIV-1 infection in Mwanza Region, Tanzania.Lancet. 1997; 350: 1805-1809Summary Full Text Full Text PDF PubMed Scopus (142) Google Scholar Ensuring prompt and effective treatment for all individuals with symptomatic infections is a challenge for health-care providers, especially with the development of antimicrobial resistance. Already, resistance in Neisseria gonorrhoeae is problematic and is emerging in Haemophilus ducreyi (see p s8). Ensuring prompt and effective treatment for symptom-free individuals, however, is an even bigger challenge and will require the development of new diagnostic tools that not only can detect symptomless infections but are rapid, non-invasive, easy to use, and inexpensive. Even with improved STD treatment and prevention activities, individuals will remain whose initial infections were not diagnosed or treated appropriately. As a result, improving the diagnosis and clinical care of their complications and sequelae should be part of any comprehensive STD programme. Evidence based on trends in reported cases suggests that public-health programmes have been effective in reducing the incidence of STDs. However, such trends need to be interpreted with caution, because differences in reported cases may reflect changes in how data were collected and access to care rather than a change in incidence. Despite this caveat, the data suggest grounds for optimism. For example, in Norway, the number of reported cases of gonorrhoea fell from more than 10 000 in 1981 to less than 300 in 1993.15National Institute of Public Health (Norway) MSIS report. NIPH, Oslo1993Google Scholar In Costa Rica, Chile, Zimbabwe, and Thailand, steady and sustained declines in reported STD cases have also been documented following active prevention programmes.16PAHO/WHO AIDS, HIV & STD annual surveillance report for the Americas. 1992Google Scholar, 17Ministry of Health and Child Welfare (Zimbabwe) National AIDS Coordination Programme Annual Report. MHCW, Harare1995Google Scholar, 18Hanenberg RS Rojanapithayakorn W Kunasol P Sokal DC Impact of Thailand's HIV-control programme as indicated by the decline of sexually transmitted diseases.Lancet. 1994; 344: 243-245Summary PubMed Scopus (374) Google Scholar Reduction of the prevalence and burden of disease associated with STDs requires a concerted effort by national public-health services, international and bilateral agencies, nongovernmental organisations, the private sector, and research institutions. A comprehensive, multifaceted strategy is required, which can address a problem that originates in the complex web of social and biological systems. Primary and secondary prevention programmes need to be strengthened and integrated into health systems, and must be accessible to all. Key elements of these programmes include: first, health-promotion approaches aimed at empowering individuals and communities to avoid situations of risk in their specific social context; second, improved access to and quality of STD services including screening for curable STDs; third, improved access to technologies that people can use to prevent infection (eg, condoms); fourth, reduction of the stigma associated with STDs;19WHO/UNAIDS Sexually transmitted diseases: policies and principles for prevention and care. WHO, Geneva1997Google Scholar and, finally, improved surveillance. More research will also be required to improve this process, mainly directed at increasing our knowledge of the distribution of these infections, the link between infection and the development of different complications, and the role played by different factors (eg, genetic, environmental, and cultural) in the development of complications.