A city’s sewage holds a treasure trove of information about its citizens. And now, what all that waste shows about COVID-19 is available for the whole internet to see.

On Friday, the CDC announced the launch of a new COVID data portal. The wastewater surveillance map shows how COVID levels in a population’s refuse change over time in the 232 sites where that data is collected. The CDC says that data can indicate whether COVID levels are going up or down in sewage, which has been proven to correlate with an area’s overall COVID levels.

If a person has contracted COVID-19, it’s common for the virus’s RNA to show up in that person’s waste — the CDC says this occurs in 40-80 percent of infected people. This viral “shedding” can happen before a person even starts showing actual symptoms. So the CDC and its municipal partners have realized that monitoring wastewater is a useful way of forecasting COVID trends.

The CDC has been monitoring this data since the beginning of the pandemic. But it has expanded the effort, called the National Wastewater Surveillance System (NWSS), in more sites around the country. And now the federal agency has moved to make the data available to the public.

“What started as a grassroots effort by academic researchers and wastewater utilities has quickly become a nationwide surveillance system with more than 34,000 samples collected representing approximately 53 million Americans,” Dr. Amy Kirby, the NWSS program lead, said in a press briefing Thursday.

On the map, you can zoom in to municipalities all over the country to see how their COVID levels in poo are changing. The bluer an area’s dot, the more COVID is decreasing. A red dot means that area’s sewage is more COVID-y. The proof is in the poop!