These maps from AIDSVu, a group that turns annual HIV infection rates data from the U.S. Centers for Disease Control (CDC) into interactive displays, show exactly where new cases were diagnosed between 2008 and 2011—information that the CDC has never mapped before, and which has big implications for public health.

“It’s a great indicator of where to do testing, where to put centers. We might use this data to say, ‘How many resources do we need to help link people into HIV care,” suggested Patrick Sullivan, a professor at Emory’s school of public health and the head of AIDSVu. “Or, what is the growth in HIV load going to look like in the future, to plan for provider capacity?” The maps display cases by county, and show that 92 percent of new diagnoses between 2008 and 2011 took place in just 25 percent of U.S. counties.

In the past, the CDC, and therefore AIDSVu, have only had maps showing the number of people living with HIV and AIDS in different parts of the country. The new diagnoses data could prove a better tool to combat the rising numbers of infections—especially as tight budgets whittle away at public health efforts down to the most efficient programs. The national HIV/AIDS strategy President Obama released in 2010 emphasizes the need “to intensify in communities where HIV is most concentrated,” says Sullivan.

Above all, Sullivan hopes the brightly colored maps will remind people of the roughly 1.2 million Americans currently living with HIV. “Many people don’t have a clear understanding of how heavily impacted some parts of the U.S. are,” he says. “Sometimes it’s just about getting a view.”

Correction: A previous version of this article stated that the CDC hadn't previously collected data on the location of new HIV cases; it had collected the data, but never mapped it. This article has been updated elsewhere for clarity.