Sexually Transmitted Diseases
Syphilis, gonorrhoea and chancroid are generally considered as the main sexually transmitted diseases (STDs), but a wide variety of pathogens also are sexually transmissible, including Herpes simplex virus type 2 (HSV-2), Chlamydia trachomatis, human papillomaviruses (HPV), human T lymphotropic virus type 1 (HTLV-1), human immunodeficiency virus (HIV), and hepatitis B virus (HBV). Women, particularly adolescents, are disproportionately vulnerable to STDs, many of which remain asymptomatic, favouring spread of infection. The risk of acquiring an STD is highest in urban areas, in low socioeconomic groups, in the young, and in association with illicit drug use and prostitution. In the USA, as an example, rates of gonorrhoea and syphilis are greater for African Americans and Hispanics than in the non-Hispanic white American population, and African American and Hispanic women suffer a greater share of severe complications of these diseases, such as pelvic inflammatory disease (PID) caused by bacterial infections, and cervical cancer caused by HPV infection.
Apart from the HIV epidemic, STDs cause significant morbidity and contribute greatly to increasing health-care costs. Several common STDs adversely affect pregnancy, causing spontaneous abortions, stillbirths, preterm delivery and postpartum endometritis. Neonatal infections include gonococcal conjunctivitis which may lead to blindness, chlamydial pneumonia which may lead to chronic respiratory disease, and herpes encephalitis. Genital infection with HPV is causally associated with cervical cancer, the most common cause of cancer-related death in women throughout the world. For this reason, HPV will be discussed in Chapter 8 (see 8.3.). A consensus has emerged that the prevention and control of STDs require a global initiative, the success of which will largely depend on the development of safe and effective vaccines. Currently, except for hepatitis B infection, no such vaccines exist.