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Its expansion was frighteningly fast. A handful of cases were first recognized in the U.S. at the beginning of the 1980s, but AIDS was soon seen around the world.
By 1990, the world had a pandemic on its hands. In 1997, the peak of the epidemic, more than 3 million people became newly infected with HIV.
Then science struck back. Drugs approved for HIV treatment in the mid-1990s proved profoundly effective, transforming AIDS from a death sentence to a chronic illness. Those treatments, combined with an international commitment to manage the disease by providing access to free drug therapy, led to a steep drop in new HIV infections.
The United Nations has kept track of HIV worldwide for the past couple of decades. Below, we use that data to explore some of the trends in HIV prevalence. (The chart shows the percentage of the population, ages 15 to 49, living with HIV.)
There are some holes in the data — notably, no yearly estimates for China, Brazil or Ethiopia. Regional percentages reflect only the countries where HIV prevalence was recorded.
Developing countries without a substantial health care infrastructure or the resources for educational campaigns have been the hardest hit by the AIDS epidemic. But many developing nations have stepped up HIV prevention and treatment in the past decade, leading to some notable successes.
Sub-Saharan Africa remains the hardest-hit region. In South Africa, about 1 in 5 adults is infected. In Botswana, it's 1 in 4.
While the number of HIV cases in the region more than doubled in the past two decades, it's not all bad news. In the past 10 years, the U.N. says, the number of new HIV infections dropped by more than 25 percent in 22 countries in the region, including some with the largest number of infected people: Zimbabwe, Ethiopia, Zambia, Nigeria and South Africa.
It might surprise you to see that countries with GDPs greater than $10,000 per capita entered the 1990s with higher HIV prevalence than many of their poorer neighbors. That's largely attributed to the extent of the epidemic in the United States. In the past 20 years, these wealthier nations have seen a slight but steady rise in the prevalence of HIV.
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