CHICAGO (CBS) — The Illinois Department of Public Health has teamed up with health facilities around the state to offer free and anonymous screenings for National HIV Testing Day.

Among Chicago locations offering free, walk-in testing for the virus that causes AIDs are The Howard Brown Health Center and Ruth M. Rothstein CORE Center.

The health department wants people to be tested for HIV because many people infected with the virus don’t know they have it.

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The Centers for Disease Control and Prevention estimates that 1.1 million Americans are living with HIV and more than 20 percent of people don’t know they’re infected.

Illinois has the seventh-highest number of AIDS cases in the nation, with more than 41,000 reported cases since 1981.

The Illinois Department of Public Health recommends that sexually active people be tested once a year and those who engage in risky behavior be tested more often.

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