Using aggregated public data from a survey conducted by Carnegie Mellon University, Facebook on Monday released its first county-by-county map of the US showing prevalence of self-reported COVID-19 symptoms, adding that such maps will soon be released for other countries globally to prevent the spread of the deadly disease.

The US map shows an estimated percentage of people with COVID-19 symptoms, not confirmed cases.

According to Facebook, the maps, which will be updated daily, are meant to help health officials allocate resources and decide where parts of society can be reopened.

"Facebook doesn''t receive, collect or store individual survey responses. This map is not intended for diagnostic or treatment purposes, or for guidance on any type of travel," said the social networking giant.

Carnegie Mellon University''s (CMU) Delphi Research Center on Monday made public the initial results of their US symptom survey that was promoted on Facebook.

Ryan Tibshirani, co-leader of Carnegie Mellon''s Delphi COVID-19 Response Team, said millions of responses to CMU surveys by Facebook and Google users are providing the team with real-time estimates of disease activity at the county level for much of the United States.

"I''m very happy with both the Facebook and Google survey results. They both have exceeded my expectations," Tibshirani, associate professor of statistics and machine learning, said in a separate statement.

The survey results, combined with data from additional sources, provide real-time indications of COVID-19 activity not previously available from any other source.

CMU launched its COVIDcast site, featuring estimates of coronavirus activity based on those same surveys from Facebook users.

Later this week, the COVIDcast site will debut interactive heat maps of the United States, displaying survey estimates from not only Facebook, but also Google users.

The maps also will include anonymized data provided by other partners, including Quidel Corp. and a national health care provider.

Most of the data sources are available on a county level and the researchers say they have good coverage of the 601 US counties with at least 100,000 people.

Within a few weeks, they expect to use these estimates to provide forecasts that will help hospitals, first responders and other health officials anticipate the number of COVID-19 hospitalizations and ICU admits likely to occur in their locales several weeks in advance.

To date, CMU is receiving about one million responses per week from Facebook users. Last week, almost 600,000 users of the Google Opinion Rewards and AdMob apps were answering another CMU survey each day.

To aid in COVID-19 forecasting, Facebook each day invites some of its US users to voluntarily answer a CMU survey about any COVID-19 symptoms they might be experiencing; the survey is controlled by CMU and individual responses are not shared with Facebook.

Likewise, Google is helping CMU distribute one-question surveys to its users and results also are not shared with Google, said CMU.

Facebook CEO Mark Zuckerberg said the goal is to give state officials a sense of where they may need to direct resources, such as personal protective equipment, or PPE.

Zuckerberg wrote in the Washington Post about how surveys like this can be an important tool in fighting COVID-19 and announced that Facebook is working with faculty from the University of Maryland to expand the programme globally.

"I think providing aggregate data to governments and health officials is one of the most important tools tech companies can provide," Zuckerberg said.