President Trump announced early Friday that he and first lady Melania Trump have tested positive for the novel coronavirus, raising the question of who they came in contact with while infectious and who now needs to be tested or enter a period of quarantine.

White House aide Hope Hicks' diagnosis is what reportedly prompted the president and first lady to get tested.

In any case, swift, successful contact tracing is key to alert individuals of possible coronavirus exposure and help interrupt the chain of transmission.

In New York State, for example, hired contact tracers use software to collect data on virus spread. They then reach out to those positive for COVID-19 through a phone call.

“The Tracer will work with you to identify and reach out via phone and text to anyone you’ve been in contact with while you were infectious to trace and contain the spread of the virus," per the state's webpage.

Cooperation with contact tracers is key in helping to interrupt the chain of virus transmission. (iStock)

Cooperation with contact tracers is key in helping to interrupt the chain of virus transmission. (iStock)

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Contact tracing can be difficult. According to a recent analysis of contact tracing efforts in North Carolina, nearly half of coronavirus patients in a given county did not report contacts, and when contacts were given, a quarter of them were unreachable, according to a report from the Centers for Disease Control and Prevention (CDC).

“Despite aggressive efforts by health departments, many COVID-19 patients do not report contacts, and many contacts cannot be reached,” said the CDC report. “Improved timeliness of contact tracing, community engagement, and community-wide mitigation are needed to reduce SARS-CoV-2 transmission.”

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The agency offered several explanations for the poor cooperation: a phone call hindered contact tracers’ ability to establish rapport; COVID-19 patients didn’t want close contacts to enter quarantine and possibly suffer job- or financial-related consequences; or finally, perhaps contacts were hesitant to answer phone calls from unknown numbers.

Meanwhile, as President Trump and the first lady quarantine, a senior White House official told Fox News' Peter Doocy that White House chief of staff Mark Meadows has tested negative. Meadows was tested “as part of normal protocol,” Doocy said.

"We've tested all of our core staff," Meadows told reporters Friday, adding that "the president does have mild symptoms."

“There have been some things swirling around online about next steps; people wanting to know who might have been in contact with the President and with Hope Hicks,” Doocy added, raising questions about former Vice President Joe Biden’s possible exposure given his proximity to the president on the debate stage Tuesday night.

Biden has since confirmed that he and his wife, Jill, have tested negative. The Biden campaign told Fox News that Biden's running mate, California Sen. Kamala Harris, was tested Thursday, as part of the campaign's routine testing, and tested negative.

Vice President Mike Pence and second lady Karen Pence tested negative for COVID-19 on Friday, hours after President Trump, first lady Melania Trump and White House adviser Hope Hicks confirmed they'd tested positive for the virus.

“As has been routine for months, Vice President Pence is tested for COVID-19 every day. This morning, Vice President Pence and the Second Lady tested negative for COVID-19,” Pence Press Secretary Devin O’Malley tweeted. “Vice President Pence remains in good health and wishes the Trumps well in their recovery.”

Fox News’ Adam Shaw, Paul Steinhauser and Peter Doocy contributed to this report.

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