In an effort to help state health officials identify growing hot spots around the nation where testing may not be especially widespread, Facebook has partnered with Carnegie Mellon University to produce a county-by-county map of the U.S. showing the percent of the population reporting flu-like or coronavirus symptoms.

"Overall, since experiencing symptoms is a precursor to going to the hospital or becoming more seriously ill, these maps could be an important tool for governments and public health officials to make decisions on how to allocate scarce resources like ventilators and PPE, and eventually when it's safe to start re-opening society," writes CEO Mark Zuckerberg in a statement.

As NBC News reports, Facebook has been prompting users to report any symptoms on the site, via a voluntary survey. "Every day, a new sample of Facebook users over 18 years old within the United States are invited to participate in the survey," Facebook says on the map site. "Facebook doesn’t receive, collect or store individual survey responses, and CMU doesn’t learn who took the survey."

Still, these maps, along with others that use Facebook co-location data to show people's interconnectedness between U.S. towns and cities, and one that shows range of movement of individuals in a city, have some privacy advocates worried. The data is aggregated and anonymized, and Facebook says that it has taken steps so "datasets can show information at a city or county level, not the patterns of individuals." Still, does Facebook have any credibility when it comes to privacy?

Two weeks ago, when Facebook unveiled its "Data for Good" program, the company said that it hoped its trove of location-based data could help public health officials better understand if social-distancing mandates are working, and where they're working.

Also on Monday, Facebook announced that it would be removing some users' posts and event listings promoting protests of stay-at-home orders. As CNN reports, the company has come under fire as the platform is being used by largely pro-Trump and anti-government groups in multiple states that are looking defy state orders for social distancing — and Trump himself has oscillated between encouraging these groups and saying that governors should decide when orders are lifted.

The latest map shows relatively low symptom reporting around the Bay Area — San Francisco and Santa Cruz County are the only two nearby locales with more than 1% (1.4% and 1.55% respectively) of survey takers reporting symptoms. As of Monday, San Francisco has 1,216 confirmed cases of COVID-19 to date, representing just one-tenth of a percent of the city population. And, by comparison, Manhattan (New York County) has 1.45% reporting symptoms, with somewhat higher numbers currently in nearby Queens, Kings, and Bronx counties.

But potential hot spots are appearing on Facebook's map like Navajo County, Arizona; Natrona County, Wyoming; and Churchill County, Nevada, where 3.7%, 2.29%, and 1.66% of people were reporting symptoms in the last week.

Facebook has not said how many people have responded to its voluntary surveys so it is unclear how broad a data set the map is based on.

As NBC News notes, former Facebook employees Mike Krieger and Kevin Systrom, the co-founders of Instagram, launched their own COVID-tracking tool last week. It's called Rt.live, and it tracks where the coronavirus is spreading the most on a given day, state by state. The name refers to the R_t figure used by epidemiologists to measure the average number of people who become infected by an infectious person. At the moment, North Dakota leads the country with the highest R_t level of 2.2 — this is one of several states, a few of which like Nebraska also have high R_t numbers right now, where governors have resisted imposing strict social distancing mandates. California's rank is presently 1.1, near the middle of the pack, while New York State has brought its level down to 0.45, the third lowest in the country after Connecticut and Michigan.