INDIANAPOLIS (AP): State health officials are urging Indiana residents to get tested for the human immunodeficiency virus as part of National HIV Testing Day.

That day is being observed on Monday this year.

More than 540 Indiana residents were diagnosed in 2015 with HIV, which can develop into AIDS.

The virus has no cure and can be contracted through blood and other bodily fluids. Intravenous drug users and people who have unprotected sex are the most at risk to contract the virus.

The Indiana State Department of Health says getting tested is a good idea because nearly 13 percent of people who live with HIV in the U.S. don’t know they have it.