The White House and the Centers for Disease Control and Prevention are asking Facebook, Google and other tech giants to give them greater access to Americans' smartphone location data in order to help them combat the spread of the coronavirus, according to four people at companies involved in the discussions who are not authorized to speak about them publicly. Federal health officials say they could use anonymous, aggregated user data collected by the tech companies to map the spread of the virus - a practice known as syndromic surveillance" - and prevent further infections. They could also use the data to see whether people were practicing "social distancing." The federal effort [was] first reported by The Washington Post. The government officials have held at least two calls in recent days with representatives from the companies, the sources said. Those officials are "very serious" about making this happen, a person at one of the tech companies said. Similar and more aggressive surveillance practices have already been put to use in China, South Korea and Israel. The moves have set off alarm bells among privacy advocates who fear what the government may do with users' data. Facebook already provides health researchers and nongovernmental organizations in some countries with anonymized data to help disease prevention efforts. Representatives from Facebook, Google, Twitter, Apple, Amazon, Microsoft, IBM and Cisco all took part in the call with White House and federal health officials.