sexually transmitted diseases

sexually transmitted diseases were previously called ‘venereal diseases’, of which there were three: syphilis, gonorrhoea, and chancroid. Over time, but particularly during the second half of the twentieth century, the range of diseases spread by sexual contact have increased considerably, and include infection by a variety of organisms, particularly bacteria and viruses, of which the newest is the Human Immunodeficiency Virus, causing AIDS (see table).

Currently, the geographical distribution of the sexually transmitted diseases (STDs) varies in number and type of condition. The World Health Organisation (WHO) estimates 333 million new infections per year (excluding HIV/AIDS). The major focus is South and South-East Asia, with an estimated 150 million new cases in 1995, and sub-Saharan Africa, with 65 million. In the developing world, the commonest diseases are gonorrhoea, syphilis, chancroid, and HIV infection, whereas in developed countries they are chlamydial infections, non-specific urethritis, genital warts, and herpes.

The STDs are important because of their complications and social stigma. The most serious sequelae occur in women, and are pelvic inflammatory disease (infection in the fallopian tubes) and ectopic pregnancy (pregnancy in the tubes), but the infections also increase the risk of stillbirth and prematurity, and can affect the new-born baby. In sub-Saharan Africa, 50% of cases of infertility can be attributed to prior tubal infection, usually with gonorrhoea or chlamydia.

Microorganisms that can be sexually transmitted

Bacteria	Chlamydia trachomatis
	Neisseria gonorrhoeae
	Gardenerella vaginalis
	Treponema pallidum
	Group B Haemolytic streptococcus
	Haemophilius ducreyi
	Calymmatobacterium granulomatis
	Shigella species
Viruses	Herpes simplex virus types 1 and 2
	Wart virus (papillomavirus)
	Molluscum contagiosum virus
	(poxvirus)
	Hepatitis A, B, and C virus
	Cytomegalovirus
	Human immunodeficiency
	virus 1 and 2
Mycoplasmas	Ureaplasma urealyticum
	Mycoplasma hominis
Parasites	Sarcoptes scabiei
	Phthirus pubis
Protozoa	Entamoeba histolytica
	Giardia lamblia
	Trichomonas vaginalis
Fungi	Candida albicans

The risk of acquiring a sexually transmitted infection is related to a number of factors, which include demography, partner change, poverty, urbanization and migration, social unrest, and war, as well as lack of diagnostic and treatment facilities.

The diseases and their features

The three most common presenting symptoms of STDs are urethral discharge, genital ulceration, and vaginal discharge. Whereas the first two are usually due to an STD, vaginal discharge is not. Most women have a physiological vaginal discharge, which can vary from day to day, and can also be related to their menstrual cycle. It can be due to other infections, such as candida (thrush), which are not usually sexually transmitted. Pointers to the possibility that a vaginal discharge is due to an STD are development of symptoms after a recent partner change, recent multiple sexual contacts, symptoms that are recurrent or persistent, and symptoms in the woman's partner. Finally, there may be general symptoms such as abdominal pain, menstrual problems, or pain on intercourse.

Gonorrhoea, non-specific genital infection, and chlamydia

In heterosexual men, these conditions give rise to discharge from the penis, 3–14 days after exposure. In homosexual men, the rectum can be infected, but in many incidences the patient is unaware of this unless they attend a clinic for a routine check-up, or at the request of a partner who develops symptoms. In women, these three conditions can often be without specific symptoms, especially since vaginal discharge is common. These infections are particularly important in women because of the complication of pelvic inflammatory disease; if this arises, it usually causes abdominal pain, perhaps with menstrual disturbances, and pain on intercourse. Women may only become aware of their infection when their male partner develops problems. Gonorrhoea can be treated with penicillin, and non-specific genital infection and chlamydia with tetracycline.

Genital warts

— small lumps around the genital regions — have become increasingly common. They have a very long incubation period after exposure (anything up to 6 months). Treatment is straightforward, by freezing or applying acidic substances such as podophyllin. Warts tend to recur. It is important that they are treated, particularly in women, where there is a possible association between some types of warts and the later development of carcinoma of the cervix. All women with genital warts should have regular cervical smears.

Genital herpes

is a viral condition with a short incubation period of approximately 3–7 days. If it is a first attack, the symptoms can be particularly severe, with pain, and blisters breaking down into sores, which sometimes can be extensive. Occasionally patients may have a temperature and headache, and feel generally unwell. There are two types of herpes simplex virus. Herpes type 1 normally causes cold sores, but oral–genital contact can transmit this from the lips to the genital area, therefore one should avoid this type of contact with people during the time that they have cold sores. There is no cure for this condition, and it tends to recur, but with unpredictable frequency from patient to patient. Pregnant women can pass herpes on to the baby at the time of delivery, so they should be under specialist care.

Syphilis

is now very uncommon in the UK. Primary syphilis occurs after an incubation period of about 9–90 days. Usually a solitary, painless ulcer appears at the site of exposure (penis, vulva, rectum, etc.). This will heal without treatment. Secondary syphilis appears 4–8 weeks later, in the form of a widespread rash, mainly on the shoulders, chest, back, abdomen, and arms. Tertiary syphilis occurs any time from 3–20 years after exposure, with complications affecting the central nervous system and heart.

Candidiasis, trichomonas, and bacterial vaginosis

cause vaginal discharge, and are not usually sexually transmitted.

Genital ulcers

are not necessarily due to STD. In Britain the commonest causes are genital herpes and syphilis, but in tropical countries there are other conditions commonly causing genital ulceration.

HIV and AIDS

Even though North America and Europe experienced the first impact of the AIDS epidemic, infections with HIV are now seen throughout the world, with the focus having switched to developing/resource-poor countries. WHO estimate that, by the end of 2000, 36.1 million people were living with HIV/AIDS, and that 5.3 million new infections occurred during that year. At the time of writing, 90% of all infections occur in developing countries and continents, with the major brunt of the epidemic in sub-Saharan Africa (22.5 million cases), and south and south-east Asia (6.7 million cases).

It is now realized that cases of AIDS were first seen in central Africa in the 1970s, even though at that time it was not recognized as such. Current surveys from some African countries show that the level of infection is high amongst certain groups: in 50–90% of prostitutes and 30% of those attending departments for STDs and antenatal clinics. The advent and increase of HIV infection since the 1980s has highlighted the importance of infections spread by the sexual route. It has also been recognized that the presence of a sexually transmitted disease, particularly (a) genital ulcer(s) and/or a vaginal/urethral discharge, can enhance both the acquisition and transmission of HIV by increased shedding of the virus within and from the genital tract.

The most common mode of transmission of this virus throughout the world is by sexual intercourse, vaginal or anal. Other methods of transmission are through the receipt of infected blood or blood products, semen, or donated organs; and through the sharing or re-use of contaminated needles by injecting drug users, or for therapeutic procedures. Also, transmission from mother to child can occur, in the womb, possibly at birth, or through breast milk.

Acute infection with HIV usually passes unnoticed, although there may sometimes be fever, swollen lymph nodes, muscular pain, and a rash. Most patients are unaware of their infection unless they are tested. The antibody test carried out on blood can take approximately three months to become positive (the window period). In view of this, patients are encouraged to delay being tested after possible exposure. Chronic infection follows and again the patient may not be aware that they are infected — or they may have non-specific symptoms such as fever, night sweats, diarrhoea, and weight loss. The time between infection with HIV and developing AIDS can be very long: on average about 8–9 years. Once a patient develops AIDS, they can have tumours and/or infections in various parts of the body. There is no cure for AIDS, but the infections can be treated, and new antiviral agents against HIV are now more powerful, and may alter the medical history and life expectancy of those infected.

Control of sexually transmitted diseases

is served in the UK by a network of specialist clinics: departments of Sexually Transmitted Diseases or Genitourinary Medicine clinics. The image of such clinics has changed considerably; they have become more friendly, with far less associated stigma. Most people attend without medical referral, and because the remit of these clinics has extended in recent decades, many use them for check-ups, screening for HIV, and for gynaecological problems or contraceptive advice. In developing countries, such specialist services do not usually exist, and sexually transmitted diseases are normally managed in non-specialist services, usually in rural primary health centres by non-medical staff.

Prevention of STDs involves primary and secondary approaches. Primary prevention aims to educate individuals about the advantages of discriminate and safe sex (prevention by the use of condoms), about the symptoms of the common sexually transmitted diseases, and about how to seek care for them. It is also important to point out that some conditions may cause no symptoms, so that regular check-ups are advised for those who often change their partners.

Secondary prevention aims to encourage people to seek care without delay once the symptoms of a disease are recognized, to stop sexual intercourse until medical advice has been sought, and to adhere to the advice and treatment given. The final aspect of control is the tracing of the sexual contacts of the infected patient, who may have infection without being aware of it.

M. W. Adler

Bibliography

Adler, M. W. (1980). The terrible peril — a historical perspective on the venereal diseases. British Medical Journal, 281, 206–11.
Adler, M. W. (1997). The ABC of AIDS, (4th edn). BMJ Publications, London.
Adler, M. W. (1999). The ABC of sexually transmitted diseases, (4th edn). BMJ Publications, London