One thousand blocks of the Aids Memorial Quilt are displayed at the Ellipse on June 26, 2004 in Washington, D.C. (Shaun Heasley/Getty Images)

Tuesday marks the twenty-first World Aids Day, and will be marked by global events around the world to try to raise awareness about HIV and AIDS prevention.

HIV causes AIDS by destroying or injuring immune system cells, which systematically makes the body unable to fight off infections and other ailments, according to the U.S. Department of Health.

According to California’s Kaiser State Health, there were 148,949 AIDS cases reported in California at the start of 2008. The figure accounts for about 14.4 percent of the U.S. population affected. The New York rate of AIDS infections is even higher, at 181,461 cases, or 17.6 percent of those affected in the nation. Other states with a sizable infected population include Florida and Texas.

The overall rate in 2006 was 18.5 persons per 100,000 people, according to the most recent Center for Disease Control (CDC) findings. This amounts to 1,018,428 people infected in the United States, says the CDC. African-Americans had a significantly higher rate than whites—almost eight times the rate, says the report.

The disease has been more devastating for males than females—74 percent of those affected are male. Cumulatively, 562,793 people have died in the U.S. as a result of the virus, says the CDC.

Various states throughout the U.S. will have events marking the anniversary.

In the greater Washington, D.C. area, a 1,200-square foot part of the AIDS Memorial Quilt is on display at George Mason University. The quilt was made in remembrance of people who have died from AIDS. The quilt is meant to be a reminder that AIDS is still affecting people worldwide. Another 160 panels of the quilt will be shown in Asheville, N.C.

The construction of the quilt began in 1987 in San Francisco to raise awareness of the disease, according to the Aids Memorial Quilt website. Now, there are more than 44,000 panels that constitute the quilt.

However, the World Health Organization says that the worldwide trend for HIV infections has gone down 17 percent in the past eight years. 33.4 million people worldwide are infected with the disease.

"The good news is that we have evidence that the declines we are seeing are due, at least in part, to HIV prevention,” said Michel Sidibe, Joint United Nations Program on HIV/AIDS executive director in a recent World Health Organization report. Sidibe added that more resources need to be allocated to worldwide AIDS/HIV prevention programs.

In the U.S., the rate of AIDS infection has seen a slight decrease since 2003 levels, say recent statistics from the CDC.