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Sexually Transmitted Diseases: Detection, Differentiation, and Treatment

James R. Clark, MD


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In Brief: Sexually transmitted diseases (STDs) are very common in the young, athletic population. Many STDs cause no symptoms, but even when symptoms occur it can be difficult to distinguish between two different infections. Sexual history, current complaints, physical examination, and laboratory tests are all important in determining the cause. Pharmacologic treatment differs by disease, whether or not the patient is pregnant, and, in some conditions, on the stage of the disease. Prevention is as important as treatment, and all patients should be educated about prevention and the risks associated with sexual activity, especially HIV infection.

Sexually transmitted diseases (STDs) are found among every racial, ethnic, and social group, but certain groups have a higher occurrence rate. One group in which STDs are common is young athletes. Physicians who treat athletic patients, therefore, must be attuned to the signs and symptoms of many STDs and know how to differentiate among them. (Although human immunodeficiency virus [HIV] is of prime concern, the depth of information required on this complex disease is beyond the scope of this article.)

In addition to evaluating and treating patients who have STDs, physicians must make sure that patients' sexual partners are informed that they might need treatment. Patients also need to know the importance of abstaining from sexual activity while infectious.


With 4 million annual cases, chlamydial infection is the most common STD in the United States (1). As is true of most STDs, the peak incidence of genital chlamydial infection is in the late teens and early twenties. The prevalence of the disease in asymptomatic high school boys is 13.2% in one study (2) and is estimated to be 5% to 10% in university clinics (3). Chlamydia trachomatis is more difficult to transmit than Neisseria gonorrhoeae, but, like gonorrhea, it transmits more readily from a male than from a female (4).

Infection caused by C trachomatis is usually asymptomatic, especially in female patients (5). If symptoms develop, they usually occur 7 to 14 days after infection. Symptoms in women usually include vaginal discharge, dysuria, lower abdominal pain, and, occasionally, menstrual abnormalities. Complications of chlamydia include pelvic inflammatory disease (PID), perihepatitis (Fitz-Hugh-Curtis syndrome), or conjunctivitis from exposure to genital secretions.

Symptomatic male patients usually have dysuria and mild urethral discharge only but can have abrupt symptoms including swelling of the epididymis with fever and chills. In young men, epididymitis is usually caused by C trachomatis (6). It is important to rule out other causes of scrotal tenderness such as testicular torsion, acute orchitis, tumor, and hydrocele. Chlamydial infection can also cause Reiter's syndrome, which involves conjunctivitis, urethritis or cervicitis, arthritis, and mucocutaneous lesions.

Diagnosing chlamydial infection is difficult. A presumptive diagnosis can be made if there are several neutrophils per high power field and a gram-negative stain of the discharge. A Gram stain should be done to exclude gonorrhea, as should a urethral culture for C trachomatis. Other confirmatory tests include antigen detection, nucleic acid hybridization, and serology, but these are not usually ordered.

Chlamydia has been found to be susceptible to a number of antibiotics (table 1: not shown) (6). Fluoroquinolones should not be given to pregnant or lactating women or to patients under 18. All sexual partners should be evaluated and treated.


Gonococcal infection is the second most common STD in the United States, affecting approximately 1 million people (7). Most patients are asymptomatic, especially women. If symptoms occur, they are difficult to distinguish from a chlamydial infection. Complications of gonorrhea include epididymitis, pharyngitis, and PID, which can lead to infertility and ectopic pregnancy (N gonorrhoeae is the single most frequent pathogen recovered in patients who have PID4). A gonococcal infection can present with dissemination, the most common manifestation being the arthritis-dermatitis syndrome. Symptoms include polyarthralgia, tenosynovitis, purulent monoarthritis, and skin lesions. Occasionally, dissemination can lead to hepatitis, endocarditis, or meningitis.

The diagnosis of gonorrhea is made with Gram staining of discharge from the female cervix or male urethra and confirmed with culture because Gram staining in females is only 50% sensitive. Gram stain should reveal intracellular gram-negative diplococci.

Many different antibiotics have been successful in treating gonorrhea (table 1: not shown) (6). The oral fluoroquinolones offer some advantages over an intramuscular medication, including ease of administration and reduced cost. It is also important to treat for chlamydial coinfection. All partners should be treated for presumed infection. If arthritis-dermatitis syndrome develops, the patient should be hospitalized and treated with intravenous antibiotics.

Bacterial Vaginosis

Besides gonorrhea and chlamydia, other causes of vaginal discharge include bacterial vaginosis and trichomonas vaginalis (see "Managing Urinary Tract and Vaginal Infections," July 1996). Candidiasis is the most common cause of vaginal discharge and should be ruled out. Bacterial vaginosis may not be a true STD because the causative organism has been recovered in many women who have never been sexually active. On the other hand, it has been recovered in the majority of male contacts of infected women, making bacterial vaginosis a probable STD.

Bacterial vaginosis is caused by Gardnerella vaginalis, and a malodorous vaginal discharge usually is the only symptom. If a patient is not treated, complications may include PID, premature labor, chorioamnionitis, and endometritis.

Diagnosis of bacterial vaginosis is usually confirmed if three of the following signs are present: (1) clue cells (epithelial cells studded with bacteria), (2) homogenous noninflammatory discharge that adheres to the vaginal walls, (3) a pH of vaginal discharge greater than 4.5, and (4) a fishy odor after addition of 10% potassium hydroxide (whiff test) (8). A Gram stain is usually nonspecific.

Treatment involves oral metronidazole (table 1: not shown) (6). Pregnant patients should be treated with topical clindamycin. Sexual partners do not need to be treated.


Trichomoniasis is caused by the protozoan Trichomonas vaginalis. As with most STDs, many patients who have trichomonas are asymptomatic. If symptoms develop, patients usually have a profuse yellow discharge and vulvovaginal irritation on pelvic examination. Approximately 50% of patients will have punctate hemorrhages on the ectocervix ("strawberry cervix") (9). Other important signs include vaginal pH greater than 4.5 and a wet mount examination revealing motile trichomonads with surrounding neutrophils. The diagnosis of trichomoniasis vaginalis can be made by a microscopic evaluation or by culture.

Treatment of trichomoniasis involves oral metronidazole as a single dose (table 1: not shown) (6). If treatment fails, metronidazole (2 g) should be given for 3 to 7 days. Routine treatment of sex partners is recommended.

Genital Herpes

In the United States, genital herpes, syphilis, and chancroid are the most common causes of sexually transmitted genital ulcers. Herpes simplex virus (HSV), the single leading cause, affects approximately 20% of young adults (10). It is important for patients to know that genital ulcers increase the likelihood of acquiring and transmitting HIV (11).

Transmission of HSV occurs through direct contact with infected secretions. Asymptomatic people can also transmit HSV. The incubation time for HSV is 2 to 20 days. Transient vesicles appear and soon rupture to form multiple painful ulcers (figure 1: not shown). These ulcers usually last about 14 days before they resolve. Other symptoms include fever, malaise, and painful regional lymphadenopathy, especially in patients who have new-onset genital ulcers.

Once the ulcers resolve, the virus resides in the sensory ganglia and establishes latency (11). About 80% of patients with primary genital HSV will develop recurrences (12), which are usually less severe than primary infections. Besides recurrent infections, other complications include proctitis, herpetic whitlow (HSV of the finger), keratitis or chorioretinitis, encephalitis, aseptic meningitis, autonomic dysfunction, and neonatal transmission.

The diagnosis of genital herpes can be made by clinical examination but may need to be confirmed by laboratory testing. Confirmatory tests include Tzanck test, culture, antigen detection, and polymerase chain reaction. The Tzanck test has a low sensitivity and specificity, so a viral culture, which takes 2 to 4 days, may be a better option.

The standard therapy for genital herpes is acyclovir (table 2) (6). Acyclovir has been shown to shorten the duration of lesions, viral shedding, and clinical symptoms, as well as reduce new lesion formation (11). Acyclovir does not cure infection because HSV cannot be eradicated from the body. Topical acyclovir has no effect on the rate of healing of recurrent lesions but may help healing in primary infections. Acyclovir is well tolerated but occasionally may cause headaches and nausea.

Table 2. Recommendations for Treating Herpes Simplex Virus*

Indication Drug Option Dosage

First clinical episode Acyclovir 200 mg PO 5 times daily, 7-10 days or until clinical resolution is achieved
Recurrent episodes(within 48 hr of lesions) Acyclovir
200 mg PO 5 times daily, 5 days
400 mg PO TID, 5 days
800 mg PO BID, 5 days
Suppressive therapy Acyclovir
400 mg PO BID
200 mg PO 3-5 times daily

*For nonpregnant and pregnant patients. If patient is pregnant and has active lesions, consider cesarean section instead of vaginal delivery. Also, evaluate and treat sexual partners if they have lesions. Dosage should be adjusted in patients who have renal failure.

PO = orally; BID = twice a day; TID = three times a day

Because acyclovir can reduce the formation of new lesions, patients should be informed of prodromal symptoms. As many as 50% of people with recurrent disease will have a recognizable prodrome, which is usually mild pain or tingling 2 days before the lesions develop (11). Patients can be instructed to take acyclovir for 5 days when these symptoms occur.

Suppressive therapy to reduce the number of recurrent HSV infections should be considered in any person who has frequent (more than six episodes a year) or disabling genital ulcers. Suppressive therapy is recommended for 12 to 14 months before assessing for recurrence (13).


Syphilis, caused by Treponema pallidum, is the second most common cause of sexually transmitted ulcers in the United States. Unlike other STDs, syphilis has several defined clinical stages.

Primary syphilis usually develops within 3 to 5 weeks after exposure. The classic lesion (figure 2: not shown) is sharply demarcated, with rolled borders and an indurated base with cartilaginous consistency (14). The ulcer is usually associated with bilateral, nontender inguinal lymphadenopathy. An untreated primary lesion usually resolves within 6 weeks, but the lymphadenopathy can last for months.

Secondary syphilis usually begins 3 to 8 weeks after the appearance of the primary chancre. The characteristic skin lesions begin as macules on the trunk and proximal extremities but eventually become papular and pustular and can appear anywhere on the body, including mucous membranes (figure 3: not shown). Associated symptoms include sore throat, fever, nontender lymphadenopathy, headache, and myalgia. Any organ can be involved in secondary syphilis, and complications include hepatitis, nephropathy, arthritis, iridocyclitis, and periostitis.

Without treatment, secondary syphilis resolves spontaneously within 3 to 12 weeks. The patient then remains in an asymptomatic stage called latency. About 25% of these patients have relapses of secondary syphilis, while 33% develop tertiary syphilis (14).

Tertiary syphilis can be manifested by neurologic, cardiovascular, or soft-tissue or cutaneous symptoms. Neurologic involvement may include meningitis, encephalitis (general paresis), or demyelinating syndrome (tabes dorsalis). Cardiovascular involvement can include aortitis, aortic regurgitation, or aortic aneurysms. The soft-tissue signs are known as gummas, which are solitary granulomatous lesions that can affect any internal organ as well as the skin.

The diagnosis of syphilis is usually made by serology because specialized equipment is needed for microscopic examination. Serologic testing includes a nontreponemal antibody test (Venereal Disease Research Laboratory [VDRL] or rapid plasma reagin [RPR]) and a treponemal antibody test (fluorescent treponemal antibody absorption [FTA-ABS] or microhemagglutination-Treponema pallidum [MHA-TP]). For primary syphilis, the RPR becomes positive 4 to 5 weeks after infection in 80% of patients but is positive in 100% of patients with secondary syphilis (14). The RPR may become negative in tertiary syphilis as well as with treatment. The treponemal antibody test should be done to exclude a false-positive result. This test usually becomes positive 5 to 6 weeks after infection and remains positive indefinitely.

Treatment is listed in table 3 (6). All patients who have syphilis should be advised to undergo HIV testing because they are at increased risk of HIV infection.

Table 3. Recommendations for Treating Syphilis*

Syphilis Stage Drug Option Dosage

Primary or secondary Benzathine penicillin G 2.4 mu IM, single dose**
Primary or secondary with penicillin allergy Doxycycline
Tetracycline HCL
100 mg PO BID,14 days
500 mg PO QID,14 days
500 mg PO QID, 14 days
Early latent (infection present < 1 yr) Benzathine penicillin G 2.4 mu IM, single dose
Late latent or tertiary without neurosyphilis Benzathine penicillin G
Tetracycline HCL
2.4 mu IM weekly, 3 wk
100 mg PO BID, 30 days
500 mg PO QID, 30 days
500 mg PO QID, 30 days
Tertiary with neurosyphilis Aqueous crystalline penicillin G 2-4 mu every 4 hr, 10-14 days

*For nonpregnant and pregnant patients. If patient is pregnant and allergic to penicillin, desensitize and treat with penicillin. Also, evaluate and treat sexual partners if they have lesions or symptoms.

**In case of treatment failure, re-treat with weekly IM injections for 3 weeks.

PO = orally; IM = intramuscularly; BID = twice a day; QID = four times a day; mu = million units


The third most common type of sexually transmitted genital ulcer is chancroid, which is caused by Haemophilus ducreyi. The exact incidence of chancroid is unknown because of incomplete reporting and difficulty in diagnosis.

Incubation for chancroid is usually 3 to 10 days, and, unlike herpes, the condition has no prodrome. The ulcers usually are multiple and have a ragged, undetermined border surrounded by a purulent base. They tend to bleed easily and are not indurated as in syphilis. Painful, unilateral inguinal adenopathy develops in 50% to 60% of patients with chancroid (15). If the patient is not treated, the affected lymph node can become abscessed, and an inguinal ulcer may then develop (figure 4: not shown).

The diagnosis of chancroid can be made on clinical examination, but, unfortunately, many patients have atypical ulcers. If an ulcer is present, its associated signs and symptoms should be assessed to rule out herpes and syphilis. The diagnosis can be confirmed by culture, which takes 3 to 5 days.

Treatment for chancroid is listed in table 1 (not shown) (6). Symptoms usually begin to resolve within 2 to 3 days, but some ulcers may take 1 month to heal (15). Ulcers can recur and often heal without further treatment. Sexual partners of patients with chancroid should also be treated.

Genital Warts

Genital warts, also known as condylomata acuminata, are benign proliferations of the epidermis caused by one of the more than 70 serotypes of the human papillomavirus (HPV). Most HPV serotypes cause self-limiting hyperproliferative lesions, but some can cause malignant disease (types 16 and 18 cause 80% of cervical cancers found in the United States) (16). HPV 6 and 11 are the most common causes of external genital infections.

HPV infection is transmitted by close contact with an infected person, and incubation takes 1 to 6 months. Most lesions are asymptomatic, but at times they can be pruritic. Genital warts can usually be diagnosed on clinical examination (figure 5: not shown). Confirmational tests include serology, culture, and DNA hybridization.

Unfortunately, there is no effective way to treat HPV. Although many HPV lesions resolve without therapy, recurrences are common and the virus is usually not eradicated by treatment. In addition to the actual wart, the surrounding area may also be infected.

Currently available therapy includes podofilox or podophyllum resin, cryotherapy, topical 5-fluorouracil, intralesion interferon, systemic interferon, and CO2 laser. Cryotherapy, CO2 laser, and podophyllin yield similar clearance and recurrence rates (16). Systemic interferon has not been shown to be effective, but intralesion interferon in combination with podophyllin is more effective than podophyllin alone, though the combination yields a similar recurrence rate (16).

Molluscum Contagiosum

Molluscum contagiosum needs to be considered in the differential diagnosis of HPV. Its lesions are caused by sexual contact as well as via fomites and autoinoculation and range from 1 to 10 mm in diameter (figure 6: not shown). They may be solitary or grouped and have a classic umbilicated center.

Treatment consists of scraping the lesion open and removing the cheeselike content. The patient should be reevaluated about 2 weeks later for possible retreatment if a lesion or lesions still exist. Sexual partners should also be treated if they have lesions. Male patients should wear a condom during intercourse until the lesions have completely healed.

Preventive Education

The most important issues in the treatment of sexually transmitted diseases are education and prevention. Patients need to be aware of the complications of STDs as well as the possibility of HIV infection. Educating patients on the risks of sexual activity and the need to avoid high-risk behaviors is critical.

Healthcare workers need to counsel patients routinely on preventing STDs and HIV infection. It is important to obtain a sexual history to determine the level of counseling needed. Counseling should focus on abstinence and monogamy, recognition of STDs, and proper use of condoms. Such education is especially crucial among high school and college students, where STDs are very prevalent.


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Dr Clark is an internist in private practice in Phoenix. He is board certified in internal medicine and is a member of the American College of Sports Medicine. Address correspondence to James R. Clark, MD, 19424 RH Johnson Blvd, Sun City West, AZ 85375.