Trichomoniasis is caused by a single-celled parasite. Incubation time ranges from 4- 20 days.

Trichomonas infection in men is usually asymptomatic. Some men may experience pain during urination and discharge thick grayish yellow pus from the urethra. About half of the infected women also have no symptoms. Some have vaginitis with symptoms such as vaginal itching, increased vaginal discharge which is yellow and greenish with an unpleasant smell, and a burning sensation during urination and sexual intercourse.

Genital warts, unlike ordinary skin warts, are transmitted through sexual intercourse. The incubation period generally ranges from 1 month to several years, with an average of about 3 months.

The person infected with genital wart virus develops small, fleshy and pinpointed, or flat growths on the skin or mucous membrane of the genital areas. The warts will grow in size and form clusters. These clusters tend to ulcerate, bleed and become inflamed. In men, warts often appear around the prepuce, glans of the penis or the urethral opening. In women, warts are most frequently found on the vulva, labia, vagina and cervix. For those who engage in anal intercourse, warts may also be found around the anus or the perineum.

Genital herpes, caused by Herpes Simplex Virus Type II, is transmitted when herpes lesions come into contact with mucous membrane or broken skin, most commonly through sexual intercourse. Incubation period averages 5 to 20 days.

After the incubation period, the infected person develops symptoms such as fever, muscle pain, frequent urination with a burning sensation and swelling of lymph nodes, etc. There will be an itching sensation in the penis, urethra, labia or cervix, followed by the appearance of small vesicles in these areas. For those who engage in anal intercourse, vesicles may appear in and around the anus. These vesicles will soon fester and rupture to become very painful ulcers with clear exudates.

The above symptoms automatically disappear in about 3 weeks. However, the virus remains dormant in the nervous system of most of the infected people, giving rise to recurrent but milder attacks of genital herpes.

Pregnant women infected with genital herpes may transmit the virus to their babies during delivery. The mortality among infected infants is over 60%, while those survived may have widespread infections with serious complications, such as brain infection and mental retardation. Pregnant women who have a history of genital herpes should therefore inform their health care providers during antenatal check-ups. If a recurrent attack occurs near the time of delivery, a Caesarean section may be needed to reduce the risk of infecting the newborn.

Anyone suspected of suffering from genital herpes infection should seek early advice and treatment. Although there is no remedy for herpes, drugs are available to reduce the discomfort and recurrence.

Gonorrhoea is caused by a bacterium and mainly transmitted through sexual intercourse with an infected person. Symptoms usually appear around 1-14 days after infection.

Symptoms are usually more conspicuous in men, which include a yellowish, purulent discharge from the urethra, and frequent urination with a burning sensation. However, about 10% of the men experience no symptoms at all. If not treated promptly, gonorrhoea can infect other genital areas such as the epididymis, prostate and urethral glands, leading to narrowing of the urethra, difficulty in urination and even kidney failure. Those who engage in oral or anal intercourse may suffer from gonorrhoea infection of the throat and the rectum, respectively.

Gonorrhoea frequently goes undetected in women because about 50-80% of the infected women have no symptoms. Some have purulent vaginal discharge, while others experience frequent and painful urination. Gonorrhoea can cause infection of the Bartholin glands, pelvic cavity as well as fallopian tubes, resulting in infertility. Women who engage in oral or anal intercourse may also suffer from gonorrhoea infection of the throat or the rectum.

An infant may suffer from eye infections through exposure to the birth canal of infected mother. Blindness may result if the infection is not treated properly.

It is essential for a person suffering from gonorrhoea to seek early diagnosis and treatment in order to prevent serious complications and permanent damage to organs.

Syphilis is mainly transmitted through vaginal, oral and anal sex with an infected person. The corkscrew-shaped syphilis bacteria can also be transmitted from an infected mother to her baby through the placenta. Transfusion of infected blood can also transmit the disease.

Syphilis is a serious disease. If left untreated, it may lead to various complications and even death. An infected person presents varying symptoms at different stage of the disease:

Primary Stage

Incubation period ranges from 7-90 days, although most people develop symptoms in 3-4 weeks after infection. In the initial stage, painless sores appear on the genital areas. These are more easily noticed in men but not in women, whose lesions develop inside the vagina.

These lesions will disappear with or without treatment. But if untreated, the syphilis bacteria will spread to the rest of the boby and the disease will progress to the secondary stage.

Secondary Stage

About 6-8 weeks after the sores are healed, the person may develop non-itchy and painless skin rash, mouth ulcers, fever, enlarged lymph nodes or flu-like symptoms. These symptoms will eventually subside and the disease enters the latent stage.

Latent Stage

An infected person at this stage has no signs and symptoms. Syphilis can only be detected by a blood test.

Late Syphilis

Signs of the late stage may appear from several to many years after the initial infection. The syphilis bacteria will affect the heart, major blood vessels and central nervous system, causing blindness, mental illness, handicap and even death.

Syphilis is treatable. Once cured, a person can resume normal sexual activity but should still visit the doctor regularly for physical check-ups and blood tests. Prompt treatment can also prevent the disease from being transmitted from infected pregnant women to her babies.

Chlamydia is a less commonly known sexually transmissible disease. Incubation ranges from 7- 21 days.

Symptoms of Chlamydia in men include difficulty in urination and a white or clear discharge from the penis. Women may experience vaginal itching, increased vaginal discharge, pelvic or abdominal pain, difficulty in urination and abnormal vaginal bleeding. Since about 70% of women and 25% of men have no symptoms at all, it is common for infected persons to spread the disease unknowingly.

Chlamydia infection can have serious consequences for both men and women. In men, it may cause inflammation of the testes, seminal vesicle and vas deferens. In women, infection usually spreads from the uterus to the fallopian tubes, causing inflammation and adhesion of the tubes which may lead to future ectopic pregnancy or infertility. Apart from sexual contact, the disease has a high risk of transmission during childbirth. The baby of an infected mother is likely to contact the disease when it passes through the birth canal, and suffer from chlamydial conjunctivits or pneumonia.

Chlamydia infection can be easily treated with antibiotics. But if the infection leads to pelvic inflammation or infertility, then treatment will be much more complicated. It is therefore very important for an infected person to seek early and proper diagnosis and treatment.

Mycoplasma is the smallest free-living bacteria (0.2-0.8µm) without a cell wall. They can be isolated from plants, insects, animals and humans, some of them are considered normal flora of the respiratory or genitourinary tract.

Mycoplasma hominis and Ureaplasma urealyticum have been implicated in human diseases. Diseases for which they have been suspected to play an etiological role are: acute pyelonephritis, bacterial vaginosis, pelvic inflammatory disease, chorioamnionitis, postabortion and postpartum fever, respiratory distress syndrome and pneumonia in newborns, wound and joint infections, nongonococcal urethritis, prostatitis and epididymitis. U. urealyticum can be found in the cervix or vagina of 40-80% of sexually mature, asymptomatic women and M. hominis in 21-53%.

AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV). The incubation period ranges up to 7 -10 years ormore. Once infected, the virus progressively destroys the immune system so that the body is unable to defend itself against diseases. A person with HIV may remain well for several years after infection. But over a longer period of time, as the immune system is weakened, the infected person may develop particular diseases such as opportunistic infections and tumours, etc. When this happens, the person is said to have AIDS.

HIV is mainly present in blood, semen and vaginal secretions. Only a very small quantity of the virus is present in saliva. The virus does not easily pass through the intact skin but may penetrate the much thinner mucous membranes of the mouth and rectum. HIV is mainly transmitted in three ways:

• Unprotected penetrative sex where semen, vaginal secretion or blood of an infected person is contacted;
• Infection of a baby by its HIV infected mother during pregnancy, childbirth or breast-feeding;
• Exposure to the virus through open wounds or mucous membrane of the eyes, nasal and oral cavity, or by sharing contaminated needles, or transfusing infected blood or blood products.

HIV can be detected through blood tests, except within the first three months after an initial infection which is known as the window period in HIV testing. Hence to ensure an accurate test result, a person undergoing blood test for HIV must be tested again six months later. There is as yet no cure for HIV infection. However, effective treatment is now available to help slow down the progression to AIDS, prevent opportunistic infections and alleviate symptoms. Affected persons should therefore maintain a positive attitude. To minimize the risk of infections, one should avoid unsafe sexual contact, promiscuity and sharing of needles and syringes.