Thirty-three years ago, on June 5, in 1981, the Centers for Disease Control in Atlanta published a report of five cases of Pneumocystis carinii pneumonia (PCP) among previously healthy young men in Los Angeles. All of the men were described as “homosexuals” — two had died.

This was the first official mention of a disease that had no name, no known means of transmission, no treatment and no cure.

In the three decades that would follow, an estimated 78 million people worldwide would contract the disease known as HIV, and the global AIDS pandemic would claim the lives of more than 39 million people.

Today is World AIDS Day.

In what has become one of the most recognized international health days in modern history, World AIDS Day is a day to raise awareness and commemorate those who have lost their lives to one of the most destructive epidemics in recorded history.

At its peak in 1996, an estimated 3.5 million people worldwide became infected with HIV.

Today, while there is increased access to treatments for AIDS and HIV that can slow the course of the disease, there is still no known cure or vaccine.

According to the Joint United Nations Programme on HIV/AIDS (UNAIDS), about 35 million people worldwide are living with HIV, and two thirds of them live in developing countries around the world.

Globally, the number of new HIV infections continues to fall — there were 2.1 million new HIV infections in 2013, the lowest number of annual new infections since the mid-to-late 1990s. Additionally, access to treatment has become more widely available and affordable.

In 2013, around 12.9 million people living with HIV had access to antiretroviral therapy. This represents 37 percent of all people living with HIV. As a result, the number of AIDS-related deaths has declined each year from a high of 2.3 million in 2005 to 1.5 million in 2013.

Still, the most current facts around HIV infections are startling and often misunderstood:

HIV is the leading cause of death among women of reproductive age;

In 2013, 54 percent of pregnant women in low- and middle-income countries did not receive an HIV test;

In 2013, almost 60 percent of all new HIV infections among young people aged 15–24 occurred among adolescent girls and young women;

Globally, gay men and other men who have sex with men are 19 times more likely to be living with HIV than the general population;

Transgender women are 49 times more likely to acquire HIV than all adults of reproductive age;

HIV prevalence is estimated to be up to 28 times higher among people who inject drugs than the general population;

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In the United States, there are approximately 1.2 million people living with HIV, and while the number of new HIV diagnoses has remained relatively stable from 2008-2012, the numbers are still too high — especially among gay and bisexual men, blacks/African Americans, and Hispanics/Latinos.

Of the 47,989 Americans diagnosed with HIV in 2012, gay and bisexual men accounted for 64 percent of cases.

According to a 2010 study by the CDC, nearly one in five gay and bisexual men in 21 major U.S. cities are infected with HIV, and the majority of new infections are spread by people who are unaware of their own status.

In total, the CDC estimates that about 14 percent of Americans living with HIV do not know they are infected.

For more information on the fight against HIV and AIDS, visit the CDC website and UNAIDS.