Sexually Transmitted Diseases (STDs - also known as Sexually Transmitted Infections) present a major public health concern in both industrialised and developing countries. However, information about infection rates is hard to come by, especially for many developing countries. No single organisation regularly collates STD statistics worldwide, and different countries have different types and levels of reporting systems. It is thought that many reports substantially underestimate the number of new STD cases because social stigma and other factors prevent people seeking health care.
A World Health Organisation (WHO) report published in 2001 provides estimates of the extent of the world's STD epidemics as they were in 1999 (previous reports were published in 1990 and 1995). As of early 2007, there are no more recent international estimates. The 2001 report forms the basis of the data on this page.
Curable STD epidemics
The WHO estimates that 340 million new cases of syphilis, gonorrhea, chlamydia and trichomoniasis occurred throughout the world in 1999 in men and women aged 15-49 years. The largest number of new infections occurred in the region of South & Southeast Asia, followed by sub-Saharan Africa and Latin America & the Caribbean. The highest rate of new cases per 1,000 population occurred in sub-Saharan Africa.
Infection rates can vary enormously between countries in the same region and between urban and rural populations. In general, however, the prevalence of STDs tends to be higher in urban residents, in unmarried individuals, and in young adults.
Chlamydia is the most common treatable bacterial STD. It can cause serious health problems such as pelvic inflamatory disease, ectopic pregnancy and infertility if it is not treated.
It is estimated that around 92 million chlamydia infections occurred worldwide in 1999, affecting more women (50 million) than men (42 million). In the period 1995 to 1999 there was an estimated worldwide increase in prevalence of 2.8 million people.
Prevalence of chlamydia varies enormously across the world. In the 1990s, rates amongst pregnant women in Europe ranged from 2.7% in Italy to 8.0% in Iceland, while studies in South America found rates of 1.9% amongst teenagers in Chile and 2.1% amongst pregnant women in Brazil. In Asia rates among pregnant women tend to be much higher: up to 17% in India and 26% in rural Papua New Guinea. In Africa, studies amongst pregnant women have revealed rates from 6% in Tanzania to 13% in Cape Verde.
Gonorrhea is a bacterial infection. It is sexually transmitted and can infect the cervix, urethra, rectum, anus and throat. Gonorrhea is a curable STD but if left untreated can cause serious health problems such as infertility, meningitis and septicaemia.
An estimated 62.35 million cases of gonorrhea occurred in 1999, affecting more women than men.
Studies of pregnant women in Africa have found rates for gonorrhea ranging from 0.02% in Gabon to 3.1% in Central African Republic and 7.8% in South Africa. In the Western Pacific in the 1990s, the highest prevalence rates (3% or greater) were in Cambodia and Papua New Guinea. Other areas such as China, Viet Nam and the Philippines had rates of 1% or less. Between 1995 and 1999, a significant increase in gonorrhea incidence occurred in Eastern Europe, with the highest rates in Estonia, Russia and Belarus.
Syphilis is a bacterial infection that is usually sexually transmitted, but may also be passed from an infected mother to her unborn child. Syphilis is a curable STD which if left untreated can eventually lead to irreversible damage to the heart and nervous system.
An estimated 12.22 million cases of syphilis occurred worldwide in 1999 - slightly below the 1995 estimate.
In contrast to a decline in rates observed in Western Europe, the 1990s saw an alarming increase in syphilis infections in the newly independent states of the former Soviet Union. There, incidence increased from 5-15 per 100,000 in 1990 to as high as 120-170 per 100,000 in 1996.
Rates of syphilis can be very variable within just one region. Studies of pregnant women in Africa have revealed rates of 17.4% in Cameroon, 8.4% in South Africa, 6.7% in Central African Republic and 2.5% in Burkina Faso. In the Western Pacific, relatively high rates of 8% in the South Pacific, 4% in Cambodia and 3.5% in Papua New Guinea have been reported. In 1997, studies amongst pregnant women in the Eastern Mediterranean Region showed syphilis infection rates of 3.1% in Djibouti, 3.0% in Morocco and 2.4% in Sudan.
The table below shows that increases in prevalence between 1995 and 1999 were seen in Eastern Europe & Central Asia, sub-Saharan Africa and Latin America & the Caribbean; in the last of these regions, incidence more than doubled. Other regions saw a drop in the number of estimated new cases.
Sexually transmitted diseases are a major global cause of acute illness, infertility, long term disability and death, with severe medical and psychological consequences for millions of men, women and children. The WHO states that "in developing countries, STDs and their complications are amongst the top five disease categories for which adults seek health care. In women of childbearing age, STDs (excluding HIV) are second only to maternal factors as causes of disease, death and healthy life lost". The presence of an untreated STD can also "increase the risk of both acquisition and transmission of HIV by a factor of up to 10".
Unlike HIV, many STDs can be treated and cured relatively easily and cheaply if diagnosed early enough.
