As medical science has become more precise in diagnosing infectious diseases, the list of known sexually transmitted diseases (STDs) has grown. The National Institute of Allergy and Infectious Diseases (NIAID) has published separate fact sheets on some of the major STDs: chlamydial infection; gonorrhea; pelvic inflammatory disease (PID); trichomoniasis and other vaginal infections; syphilis; genital herpes; genital warts; and AIDS. NIAID has prepared this fact sheet to provide information on some of the other diseases that can be transmitted sexually:

chancroid
cytomegalovirus infection
molluscum contagiosum
pubic "crab" lice
scabies
HTLV-I and II

Although some of these diseases are less well-known in the United States than other STDs, they are still important - some are especially significant for pregnant women. Many of these infections are of serious concern for people in other parts of the world, particularly in developing countries.

Chancroid ("shan-kroid") is an important bacterial infection caused by Haemophilus ducreyi, which is spread by sexual contact. Periodic outbreaks of chancroid have occurred in the United States, the last one being in the late 1980s. These outbreaks are usually seen in minority populations in the inner cities, especially in the southern and eastern portion of the country. Globally, this disease is common in sub-Saharan Africa among men who have frequent contact with prostitutes.

The infection begins with the appearance of painful open sores on the genitals, sometimes accompanied by swollen, tender lymph nodes in the groin. These symptoms occur within a week after exposure. Symptoms in women are often less noticeable and may be limited to painful urination or defecation, painful intercourse, rectal bleeding, or vaginal discharge. Chancroid lesions may be difficult to distinguish from ulcers caused by genital herpes or syphilis. A physician must therefore diagnose the infection by excluding other diseases with similar symptoms. People with chancroid can be treated effectively with one of several antibiotics. Chancroid is one of the genital ulcer diseases that may be associated with an increased risk of transmission of the human immunodeficiency virus (HIV), the cause of AIDS.

Cytomegalovirus (CMV) is a very common virus that infects approximately one-half of all young adults in the United States. It rarely causes serious consequences except in people with suppressed or impaired immune systems or in infants, whose immune systems are still developing. The virus, a member of the herpesvirus family, is found in saliva, urine, and other bodily fluids. Because it is often found in semen as well as in cervical secretions, the virus can be spread by sexual contact; it also can be easily spread by other forms of physical contact such as kissing. Day-care center staff for children under the age of 3 are at increased risk of CMV infection and should carefully wash their hands after changing diapers. Like other herpesvirus infections, CMV is incurable; people are infected with it for life. Although the virus usually remains in an inactive state, it can reactivate from time to time.

Symptoms. In healthy adults, CMV usually produces no symptoms of infection. Occasionally, however, mild symptoms of swollen lymph glands, fever, and fatigue may occur. These symptoms may be similar to those of infectious mononucleosis.

Diagnosis. The ELISA (enzyme-linked immunosorbent assay) test is commonly used to detect levels of antibodies (disease-fighting proteins of the immune system) in the blood. A number of other blood tests can suggest a diagnosis of CMV infection, but no blood test can reliably diagnose it. Although CMV can be isolated from urine or other body fluids, it may be excreted months or years after an infection; therefore, isolation of the virus from these fluids is not a reliable method of diagnosing recent infection.

Complications. Babies can be infected with CMV in the uterus if their mothers become infected with the virus or develop a recurrence of a previous infection during pregnancy. Although most babies infected with CMV before birth do not develop any symptoms, CMV is the leading cause of congenital infection in the United States. An estimated 6,000 babies each year develop life-threatening complications of congenital CMV infection at birth or suffer serious consequences later in life, including mental retardation, blindness, deafness, or epilepsy. Investigators supported by NIAID are currently studying how the virus interferes with normal fetal development and at which stages the fetus is most susceptible to infection. Congenital CMV is the most common cause of progressive deafness in children.

When CMV is acquired after birth, or if it reactivates, it can be life-threatening for persons with suppressed immune systems, such as those receiving chemotherapy or persons who have received immunosuppressant drugs for organ transplantation. Persons with HIV infection or AIDS may develop severe CMV infections, including CMV retinitis, an eye disease that can lead to blindness.

Treatment. NIAID scientists are testing new antiviral drugs that might be effective against CMV infections. The antiviral drugs foscarnet and ganciclovir have been approved for treating people with AIDS-associated CMV retinitis.

This common viral infection most often affects young children, who pass it to each other through saliva. In adults, however, the virus is transmitted sexually, resulting in lesions on the genitals, lower abdomen, buttocks, or inner thighs. Most people with the infection do not have noticeable symptoms, although sometimes the lesions, which are painless wart-like bumps, may itch or become irritated. The lesions often heal without treatment, although physicians may sometimes scrape them off or treat them with chemical irritants.

Pubic lice (pediculosis pubis or crab lice) are very tiny insects that infest the pubic hair and survive by feeding on human blood. These parasites are most often spread by sexual contact; in a few cases, they may be picked up through contact with infested bedding or clothing. An estimated 3 million people with new cases of the infestation are treated each year in the United States.

Symptoms. The primary symptom of infestation is itching in the pubic area. Scratching may spread the lice to other parts of the body; thus, every effort should be made to avoid touching the infected area, although this may be difficult.

Diagnosis. Pubic lice are diagnosed easily because they are visible to the naked eye. They are pinhead size, oval in shape, and grayish, but appear reddish-brown when full of blood from their host. Nits, the tiny white eggs, also are visible and usually are observed clinging to the base of pubic hair.

Treatment. Lotions and shampoos that will kill pubic lice are available both over the counter and by prescription. Creams or lotions containing lindane, a powerful pesticide, are most frequently prescribed for the treatment of pubic lice. Pregnant women may be advised not to use this drug, and a physician's recommendations for use in infants and small children should be followed carefully. Itching may persist even after the lice have been eradicated. This is because the skin has been irritated and requires time to heal. A soothing lotion such as calamine may offer temporary relief.

Prevention. All persons with whom an infested individual has come into close contact, including family and close friends as well as sex partners, should be treated to ensure that the lice have been eliminated. In addition, all clothing and bedding should be dry-cleaned or washed in very hot water (125? F), dried at a high setting, and ironed to rid them of any lice. Pubic lice die within 24 hours of being separated from the body. Because the eggs may live up to six days, it is important to apply the treatment for the full time recommended.

Scabies is a skin infestation with a tiny mite, Sarcoptes scabiei. Scabies has become relatively common throughout the general population. It is highly contagious and is spread primarily through sexual contact, although it also is commonly transmitted by contact with skin, infested sheets, towels, or even furniture.

Symptoms. Scabies causes intense itching, which often becomes worse at night. Small red bumps or lines appear on the body at sites where the female scabies mite has burrowed into the skin to lay her eggs. The areas most commonly affected include the hands (especially between the fingers), wrists, elbows, lower abdomen, and genitals. The skin reaction may not develop until a month or more after infestation. During this time, a person may pass the disease unknowingly to a sex partner or to another person with whom he or she has close contact.

Diagnosis. Scabies may be confused with other skin irritations such as poison ivy or eczema. To make an accurate diagnosis, a doctor takes a scraping of the irritated area and examines it under a microscope, to reveal the presence of the mite.

Treatment. As with pubic lice, lindane is an effective treatment for scabies. Pregnant women should consult a doctor before using this product. Nonprescription remedies such as sulfur ointment also are available. Sulfur is fairly effective but may be objectionable because of its odor and messiness. Itching can persist even after the infestation has been eliminated because of lingering skin irritation. A hydrocortisone cream or ointment or a soothing lotion may provide relief from itching.

Prevention. Family members and sex partners of a person with scabies are advised to undergo treatment. Twenty-four hours after drug therapy, a person with scabies infestation is no longer contagious to others, even though the skin irritation may persist for some time. As with pubic lice, special care must be taken to rid clothing and bedding of any mites.

The human T-cell lymphotropic viruses (retroviruses), HTLV-I and HTLV-II, are uncommon in the general U.S. population. They appear to be most prevalent among IV drug users and persons who have multiple sex partners, genital ulcers, or a history of syphilis. The virus can be transmitted by blood or intimate sexual contact, and can be passed from mother to child during pregnancy and through breast milk.

Most infected persons remain healthy carriers of the virus. In rare cases, however, HTLV-I can cause adult T-cell leukemia/lymphoma (ATL), a rare and aggressive cancer of the blood. Infected persons also may develop myelopathy, a neurologic disorder that affects the muscles in the legs. In addition, researchers think that HTLV-I plays a role in the development of B-cell chronic lymphocytic leukemia. HTLV-II can cause another rare cancer called hairy-cell leukemia. Because the chances of curing ATL rely on early detection, scientists are studying protein in the blood of HTLV-I-infected persons that may help predict who will develop the disease.

Blood donations are screened routinely for HTLV-I. Because lab tests cannot easily distinguish between HTLV-I and HTLV-II, experts believe many cases of HTLV-II are eliminated from the blood supply as well.