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Global epidemiology of sexually transmitted diseases Global epidemiology of sexually transmitted diseases Urology Department, Mãe de Deus Hospital, Porto Alegre, RS 90450180, Brazil Abstract
Sexually transmitted diseases (STDs) are among the first ten causes of unpleasant diseases in young adult males in developing countries and the second major cause of unpleasant diseases in young adult women. Adolescents andyoung adults (15–24 years old) make up only 25% of the sexually active population, but represent almost 50% of allnew acquired STDs. In general, STDs are epidemics and present an enormous health and economic consequences.
An adequate screening for STDs should be done on a routine basis in every part of the world. Many STDs areasymptomatic and therefore can difficult to control. The purpose of reporting of STDs is to ensure that persons whoare infected will be quickly diagnosed and appropriately treated to control the spread of infection and also so thatpartners are notified, tested and appropriately treated. It is estimated that reported cases of STDs represent only50%–80% of reportable STD infections in the United States, reflecting limited screening and low disease reporting.
High-risk sexual behavior is a highly contributive factor of this process as it often leads to teenage pregnancies andHIV/AIDS. One possible explanation for this behavior is that people do not have enough information about the trans-mission of STDs or ignore the precautions required for safe sex. Approximately 60% of new HIV infections world-wide occur in young people. The frequency of high-risk behaviors among youths may also be influenced by oppor-tunity to engage in them, particularly the amount of time that they are unsupervised by adults. However, in diagnosingand treating these patients, we can effectively prevent the spread of HIV/AIDS. Individuals infected with STDs are5–10 times more likely than uninfected individuals to acquire or transmit HIV through sexual contact. The breakingof the genital tract lining or skin creates a portal of entry for HIV and, hence, HIV-infected individuals with otherSTDs are more likely to shed HIV in their genital secretions. To date, the condom is the most effective methodavailable for males for protection against STDs. It is important to control STDs, and prevention can be the key of thisprocess. Prevention can be achieved through education of the population, identification of symptomatic and asymp-tomatic people, and effective diagnosis and treatment of these patients and their partners. (Asian J Androl 2008 Jan;10: 110 –114) Keywords: sexually transmitted diseases; safe sex; condom; young people
1 Introduction
tries and the second major cause of unpleasant diseasesin young adult women worldwide. Adolescents and young Sex is life, but we have to be conscious of the fact adults (15–24 years old) are responsible for only 25% of that safe sex is the first premise. Sexually transmitted the sexually active population, yet they represent almost diseases (STDs) are among the first ten causes of un- 50% of all newly acquired STDs [1]. In general, STDs pleasant diseases in young adult males in developing coun- are epidemics and present enormous health and economicconsequences [2].
The data regarding incidence and prevalence of STDs Correspondence to: Dr Carlos T. Da Ros, Urology Department, are heterogeneous. The prevalence of Chlamydia tra- Mãe de Deus Hospital, Farnese St 94 room 201. Porto Alegre, RS chomatis infection in young females attending STD clinics 90450180, Brazil.
Tel: +55-51-3330-1101 Fax: +55-51-3378-9996 in 1997 and 2005 are 12.2% and 15.4%, respectively, and 15.7% and 20.5% for young males [3]. However http://www.asiaandro.com; aja@sibs.ac.cn
2008, Asian Journal of Andrology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences. All rights reserved.
Asian J Androl 2008; 10 (1): 110–114 the incidence of gonorrhea is decreasing. In 1997, the have seen an increasing rate of infection (43.5%) and it reported prevalence of gonorrhea was 123 per 100 000 is more common in women than in men (3:1). Infection people, but by 2005 it had decreased to 115.6 per 100 000 with Chlamydia trachomatis may result in urethritis, people [3]. Syphilis data for men and women show epididymitis, cervicitis, acute salpingitis, or oth er statistical differences; the incidence of infection was 3.8 cases syndromes. However, the infection is often asympto- per 100 000 men in 2002 and 5.1 cases per 100 000 men in matic in women and could result in pelvic inflammatory 2005. However, there were 1.1 cases per 100 000 women in diseases (PIDs), one of the major causes of infertility 2002 and 0.9 cases per 100 000 women in 2005 [3].
[3], once in some cases the patients stayed without any An adequate screening for STDs should be done on kind of treatment. There is a high prevalence of co-infec- a routine basis in every part of the world. Many STDs tion (50%) in patients with Chlamydia trachomatis [10].
are asymptomatic and thus can difficult to control. The As with other inflammatory conditions, infection with purpose of reporting of STDs is to ensure that those are chlamydia could facilitate HIV infection. Chlamydia can infected will be quickly diagnosed and appropriately treated be transmitted to the neonates during delivery by an in- to reduce spread of infection that partners are notified, fected pregnant woman [3]. Due to its magnitude, the tested and appropriately treated [4]. It is estimated that Center for Disease Control and Prevention (CDC) rec- reported cases of STDs represent only 50%–80% of re- ommends chlamydia screening for all sexually active portable STD infections in the United States, reflecting women less than 26 years old [2]. The benefits of screen- limited screening and low disease reporting. We have ing could be demonstrated in areas where the prevalence known for some time that 60% of patients who have one of infection and rates of PIDs are decreasing since the STD will concurrently harbor another [5]. There are screening programs began [11, 12]. Evidence is insuffi- known risk factors associated with acquisition of STDs, cient to recommend routine screening for Chlamydia including biological and behavioral factors, cultural trachomatis in sexually active young men, based on influences, lack of information about transmission and con- feasibility, efficacy, and cost-effectiveness. However, traction of STD, difficult to access prevention services, screening of sexually active young men should be con- lack of adult supervision and number of sexual partners [6].
sidered in clinical settings with a high prevalence of High-risk sexual behavior is a highly contributive fac- chlamydia (e.g., adolescent clinics, correctional facilities, tor of this process as it often leads to teenage pregnan- cies and HIV/AIDS. This behavior could occur becausepeople do not have enough information about transmis- 3 Gonorrhea
sion of STDs or because they ignore the precautionsrequired for safe sex. Approximately 60% of new HIV Gonorrhea is a sexually transmitted infection com- infections worldwide occur in young people. The fre- monly manifested by urethritis, cervicitis, and/or salpingitis.
quency of high-risk behaviors among youths may also It is the second most commonly reported STD in the be influenced by opportunity to engage in them, particu- United States [3] and an estimated 600 000 new Neis- larly the amount of time that they are unsupervised by seria gonorrhea infections occur each year [13]. Gonor- adults. Boys who were un supervised for more than rhea rates in women are slightly higher than in men. The 5 hours per week after school were twice as likely to majority of urethral infections caused by Neisseria gonor- have Chlamydia or Gonorrhea as boys who were unsu- rhea among men produce symptoms that lead them to pervised for 5 or fewer hours. Nowadays, the sexual seek a medical evaluation, but treatment might not be behavior of travelers, especially international travelers, delivered in time to prevent transmission to others.
could modify the risks of STD transmission too [7], be- Among women, several infections, including Gonorrhea, cause they can transfer some diseases form.
do not produce recognizable symptoms until complica- Another important issue is that male circumcision tions (e.g., PID) occur [2]. Infections due to Neisseria is associated with lower risk of STDs as well as HIV gonorrhea, similar to those due to Chlamydia trachomatis, transmission [8]. This advantage was first described in are an important cause of PID and consequently can lead to 1855 [9] and the indication of this surgical intervention infertility or ectopic pregnancies [3]. Because gonococcal could provide protection against STDs and lead to a lower infections among women are frequently asymptomatic, the U.S. Preventive Services Task Force (USPSTF) recom-mends that clinicians screen all sexually active women, 2 Chlamydia trachomatis
including those who are pregnant, for gonorrhea infec-tion if they are at an increased risk. Women aged < 25 Genital Chlamydia trachomatis infection is one of years are at the highest risk for gonorrhea infection [2].
the most prevalent STDs and is the most frequently re- Other risk factors for gonorrhea include a previous ported STD in the United States [3]. The last 5 years gonorrhea infection, other sexually transmitted infections, Tel: +86-21-5492-2824; Fax: +86-21-5492-2825; Shanghai, China
Global epidemiology of sexually transmitted diseases new or multiple sex partners, inconsistent condom use, commercial sex work and drug addiction [2]. On theother hand, the USPSTF does not recommend screening 5 Human papillomavirus
for Gonorrhea in men and women who are at low riskfor infection [14].
HPV is another STD with important consequences Epidemiologic and biologic studies provide strong evi- because it can lead to development of anogenital cancers.
dence that gonococcal infections facilitate the transmis- This infection is characterized by the presence of visible, sion of HIV infection [15]. The prevalence in the United exophytic (raised) growths on the internal or external States decreased 74% from 1975 to 1997, probably be- genitalia, perineum, or perianal region. However, the cause in mid-1970s a control program for Neisseria gonor- majority of HPV infections are asymptomatic, unrecog- rhea infection began [3]. Since 1997 the numbers have remained stagnant with a slight increase in 2005. These HPV infections make up approximately 15%–20% increases and decreases reflect changes in screening of the population infected with an STD. Annual inci- programs, use of diagnostic tests with different performances, dence of all types of genital HPV infection is estimated to and changes in reporting practices [16]. Gonorrhea rates have be 5.5 million in the U.S. It is estimated that 75% of declined among African Americans, but have increased in all sexually active adults become infected with some form other racial and ethnic groups since 2001. However, rates of genital HPV in their lifetime. The prevalence infected, among African Americans remain markedly higher than among by age group, was as follows: 14–19 years: 35%; 20–29 years: 29%; 30–39 years: 14%; 40–49 years: 12%; and50–65 years: 6% [20–23].
4 Syphilis
There are more than 100 types of HPV and approxi- mately 40 types are related to genital area infection [2].
Syphilis is a sexually transmitted systemic disease Types 6 and 11 are the most common and recognizable caused by Trepenoma pallidum and has a highly variable clinical course. Syphilis is a genital ulcerative disease, Types 16 and 18 are related to cervical cancer and causes significant complications if left untreated and fa- are considered high risk types. Persistent infection with cilitates the transmission of HIV [3]. The male-to-female high risk types of HPV is the most common risk factor ratio is 5/7. Untreated early syphilis in pregnant women leading to cervical neoplasia [2]. Over 99% of cervical results in perinatal death in up to 40% of cases and, if cancers have HPV DNA detected within the tumor. The acquired during the four years preceding pregnancy, leads overall prevalence of HPV types 16 and 18 was 8%. The to infection of the fetus in over 70% of cases [17]. The prevalence of HPV types 16 and 18 by age group was: rate of primary and secondary syphilis reported in the 14–19 years: 16%; 20–29 years: 10%; 30–39 years: 3%; United States decreased during the 1990s. In 2000, the 40–49 years: 2%; 50–65 years: 1% [24, 25].
rate was the lowest since reporting began in 1941 [3] In June 2006, a quadrivalent HPV vaccine was li- although the rate of syphilis in the United States declined censed by Food and Drug Administration for use in the 89.7% between 1990 and 2000, between 2001 and 2005 United States. The vaccine provides protection against this rate had increased. This increase in rates was ob- types 6, 11, 16, and 18, the most common types of HPV served primarily among men. In 2005, for the first time that cause the majority of cervical cancers. The vaccine in over 10 years, the rate of primary and secondary syphi- is indicated for females aged 9–26 years old, preferably lis among women increased from 0.8 cases per 100 000 before they become sexually active [3, 26, 27].
people in 2003 to 0.9 cases per 100 000 people in 2004[3]. Increases among men who have sex with men have 6 Herpes simplex
occurred at least since 2000 and continue through 2005.
These men have been characterized by high rates of HIV Genital herpes is a common, chronic, life-long viral co-infection and high risk sexual behavior [18, 19].
infection. Two types of Herpes simplex virus (HSV) have Patients who have syphilis might seek treatment for been identified: HSV-1 and HSV-2. The majority of cases signs or symptoms at any stage in the disease. Primary (85%–90%) of recurrent genital herpes are caused by HSV- infection is characterized by ulcer or chancre at the in- 2 although HSV-1 might become more common as a cause fection site, secondary infection manifestations include, of first episode genital herpes [2]. At least 50 million but are not limited to, skin rash, mucocutaneous lesions, people in the United States have genital HSV infection.
lymphadenopathy, tertiary infection by cardiac or oph- Approximately one million new cases of HSV-2 infection thalmic manifestations, auditory abnormalities, or gum- are diagnosed each year in the United States and the matous lesions [2]. Latent infections include those lack- majority of people infected with HSV-2 have not been ing clinical manifestations and are detected by serologic diagnosed with genital herpes. Seropositivity to HSV-2 http://www.asiaandro.com; aja@sibs.ac.cn
Asian J Androl 2008; 10 (1): 110–114 is higher in HIV-infected persons and adults of lower Centers for Disease Control and Prevention. Sexually Transmit- socioeconomic status. Most women (80%) with HSV-2 ted Diseases Treatment Guidelines, 2006. MMWR 2006; 55 (No.
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