As the COVID-19 outbreak continued to spread this week, counties in Northern California instructed their citizens to shelter in place, while governments across the nation restricted gatherings and urged people to "socially distance." Now, one researcher is using anonymized Facebook location data to help public health authorities in California understand whether people actually listened.

Andrew Schroeder is vice president of research and analysis at Direct Relief, an international disaster relief organization based in Santa Barbara. Since 2017, Schroeder has been using mapping tools developed by Facebook's Data for Good team to track population movements during natural disasters and disease outbreaks. These maps use aggregated, de-identified location data from Facebook users who have location history turned on in their Facebook apps. Some 125 nonprofits and research institutions around the world have access to them. Schroeder has used them to track evacuation efforts during California's wildfires and map the cholera outbreak in Mozambique.

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But as social distancing efforts have swept the country over the last week, Schroeder began to realize that the same tools he's used to track where people in crisis are moving could also be used to track whether they're staying put.

"This is exactly the kind of problem that this data really should be able to give you insight into," Schroeder said. "You recommended everyone not go to the bars. Did they listen to you?"

Schroeder says he spent last weekend working "literally night and day," with Facebook's input, on a tool that can use Facebook's mobility data to tell public health officials whether people are moving more or moving less in a given county. Facebook confirmed it planned to ship a California prototype of this tool to Schroeder on Tuesday. Schroeder says he plans to issue daily updates to health officials through Direct Relief's partnership with the California Department of Public Health. The Department didn't respond to Protocol's request for comment.

Schroeder hopes his work in California will at least help minimize the time officials need to spend analyzing the datasets themselves. "We don't have time for people to be confused," he said.

In his post on how Facebook is helping address the spread of COVID-19, CEO Mark Zuckerberg said the company was "looking at how people can use our services to help contribute to the broader efforts to contain the outbreak." These maps are part of that work.

The company launched a series of mapping products in 2019 to help address a data gap in how health researchers track public health emergencies. One of those tools is a mobility map that shows where aggregated groups of Facebook users are moving. In the past, researchers interested in mobility patterns have largely turned to street traffic data. But it's limited, since it doesn't account for foot traffic or how many people are in a given vehicle.

Facebook is, of course, sitting on a trove of rich location data collected from users' phones. But sharing that data, even for noble purposes, is fraught, particularly for a company like Facebook, which has experienced so many privacy scandals. Research has repeatedly shown how easy it is to find real people in even anonymized datasets. And Facebook doesn't exactly have a spotless record when it comes to sharing data with academics. It was, after all, a Cambridge University professor who sold data to the now-infamous political consulting firm Cambridge Analytica.

To mitigate the risk of exposing individuals, the mobility maps include data not about the movement of specific phones, but about the movement of an aggregate population of Facebook users in a 600-meter tile on a map. The maps don't include information about who is infected, making this mobility tracking effort far more limited than the extreme measures that countries like Israel and China have recently taken in tracking the phones of individual coronavirus patients.

The maps don't include any data culled from people's Facebook profiles, either. That's important for protecting people's privacy, Schroeder says, but it makes it difficult to determine what demographics are over or underrepresented in the dataset. It would be helpful for health officials to know, for instance, whether older populations are sheltering in place.

"There's a whole bunch of questions it can't answer," Schroeder said of the data. "I know it's a problem they're really working on, but it's really thorny."

Indeed, groups like the American Civil Liberties Union are already speaking out against government uses of this Facebook data. "We don't need high-tech Big Brother tracking right now. What public health experts are saying is that we need tests, social distancing measures, and hospitals that are prepared for what is to come. We need to get the basics right, which we're not doing," said Jacob Snow, a technology and civil liberties attorney with the ACLU of Northern California.

On Tuesday, The Washington Post reported that Facebook and other companies are in talks with the White House about providing location data to track the spread of the virus and the success of social distancing. Facebook spokesperson Mandy Sugrue told Protocol the company hasn't received any such inquiries and stressed that Facebook doesn't give data directly to governments.

The company does, however, have a "huge coalition" of researchers and academics already using Facebook data to better understand how COVID-19 is spreading. Those researchers, like Schroeder, are sharing their findings with government officials who use them to make decisions about where to focus relief efforts.

"Obviously it's quite sobering. There's a global pandemic ongoing. It's very upsetting and really humbling how difficult it's going to be to control this outbreak," said Facebook's Data for Good policy lead Laura McGorman. "At the same time, I do feel that the team at Data for Good has a unique opportunity to actively help here."

In direct response to the coronavirus pandemic, Facebook has also launched a new product called "colocation maps." These maps use mobility data to show where people from different geographic locations are most likely to cross paths. That helps researchers understand whether people living in an outbreak hot spot are likely to intersect with people from a neighborhood or town that hasn't yet been hit.

With colocation maps, researchers can rank the communities that are most at risk and recommend public health interventions around that. They can further layer on publicly available demographic data about, say, whether any of those communities happen to have a large elderly population, and prioritize those areas first.

This could help public health officials monitor the spread of the virus between their local communities the same way heads of state have monitored the spread between countries, says Shenyue Jia, a research fellow at Chapman University who's working with Direct Relief to analyze the colocation maps.

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"If there's an outbreak in place A, and place B has a strong connection with place A, people in place B should stay alert," Jia said. "And if place C has a higher population of old people, maybe this place should be more alert than others."

And according to Jia, having access to this kind of data about the relationship between communities has "never been more important."

Facebook released the first version of colocation maps in Hong Kong, and Jia has already used it to highlight hot spots using case data there. That kind of research isn't possible in the United States yet, where the Centers for Disease Control and Prevention has only released case location data at the state level.

Both Jia and Schroeder say that these maps can be important resources for government agencies, which do have access to case data. Facebook doesn't allow governments to access these mapping portals for privacy reasons, so researchers like Schroeder are a crucial conduit. Schroeder says he has already been sharing colocation maps with California public health officials himself.

As for his research on social distancing, Schroeder says the data should help public health officials better understand whether people are taking these government orders to heart.

"What it won't show you," Schroeder said, "is, what's enough?"

Only time will answer that question.