Sexually transmitted infections (STIs) are a public health issue
According to 2005 WHO estimates, 448 million new cases of curable STIs (syphilis, gonorrhoea, chlamydia and trichomoniasis) occur annually throughout the world in adults aged 15-49 years. This does not include HIV and other STIs which continue to adversely affect the lives of individuals and communities worldwide. In developing countries, STIs and their complications rank in the top five disease categories for which adults seek health care.
Infections and transmission
STIs are infections that are spread primarily through person-to-person sexual contact. There are more than 30 different sexually transmissible bacteria, viruses and parasites. Several, in particular HIV and syphilis, can also be transmitted from mother to child during pregnancy and childbirth, and through blood products and tissue transfer.
STIs are caused by bacteria, viruses and parasites. Some of the most common infections are below.
Common bacterial infections
Common viral infections
STIs without symptoms
Some STIs exist without symptoms. For example, up to 70% of women and a significant proportion of men with gonococcal and/or chlamydial infections experience no symptoms at all. Both symptomatic and asymptomatic infections can lead to the development of serious complications, discussed below.
STIs adversely affect the health of women
Untreated STIs can have critical implications for reproductive, maternal and newborn health. STIs are the main preventable cause of infertility, particularly in women.
For example, 10 - 40% of women with untreated chlamydial infection develop symptomatic pelvic inflammatory disease. Post-infection tubal damage is responsible for 30 - 40% of cases of female infertility. Furthermore, women who have had pelvic inflammatory disease are 6 - 10 times more likely to develop an ectopic (tubal) pregnancy than those who have not, and 40 - 50% of ectopic pregnancies can be attributed to previous pelvic inflammatory disease.
Infection with certain types of the human papillomavirus can lead to the development of genital cancers, particularly cervical cancer in women.
STIs and adverse outcomes of pregnancy
Untreated STIs are associated with congenital and perinatal infections in neonates, particularly in regions where rates of infection remain high.
In pregnant women with untreated early syphilis, 25% of pregnancies result in stillbirth and 14% in neonatal death – an overall perinatal mortality of about 40%.
Up to 35% of pregnancies among women with untreated gonococcal infection result in spontaneous abortions and premature deliveries, and up to 10% in perinatal deaths. In the absence of prophylaxis, 30 - 50% of infants born to mothers with untreated gonorrhoea and up to 30% of infants born to mothers with untreated chlamydial infection will develop a serious eye infection (ophthalmia neonatorum), which can lead to blindness if not treated early. Worldwide, 1000 - 4000 newborn babies become blind every year because of this condition.
STIs and HIV
The presence of untreated STIs (both those which cause ulcers or those which do not) increase the risk of both acquisition and transmission of HIV by a factor of up to 10. Prompt treatment for STIs is thus important to reduce the risk of HIV infection. Controlling STIs is important for preventing HIV infection, particularly in people with high-risk sexual behaviours.
Although many different pathogens cause STIs, some display similar or overlapping signs (what the individual or the health-care provider sees on examination) and symptoms (what the patient feels such as pain or irritation). Some of these signs and symptoms are easily recognizable and consistent, giving what is known as a syndrome that signals the presence of one or a number of pathogens. For example, a discharge from the urethra in men can be caused by gonorrhoea alone, chlamydia alone or both together.
The main syndromes of common STIs are:
STI syndromic approach to patient management
The traditional method of diagnosing STIs is by laboratory tests. However, these are often unavailable or too expensive. Since 1990 WHO has recommended a syndromic approach to diagnosis and management of STIs in patients presenting with consistently recognized signs and symptoms of particular STIs.
The syndromic approach uses flowcharts to guide diagnosis and treatment is more accurate than diagnosis based on clinical tests alone, even in experienced hands. The syndromic approach is a scientific approach and offers accessible and immediate treatment that is effective. It is also more cost-effective for some syndromes than use of laboratory tests.
The pathogens causing any particular syndrome need to be determined locally and flow charts adapted accordingly. Furthermore, regular monitoring of the organisms causing each syndrome should be conducted on a regular basis to validate the treatment recommendations.
The most effective means to avoid becoming infected with or transmitting a sexually transmitted infection is to abstain from sexual intercourse (i.e., oral, vaginal, or anal sex) or to have sexual intercourse only within a long-term, mutually monogamous relationship with an uninfected partner. Male latex condoms, when used consistently and correctly, are highly effective in reducing the transmission of HIV and other sexually transmitted infections, including gonorrhoea, chlamydial infection and trichomoniasis.
(Source: WHO Fact sheet N°110)