With data continuing to suggest New York is "flattening the curve" in the spread of the coronavirus, Gov. Andrew Cuomo said this week that the next phase in the battle for his state and others is on the horizon: contact tracing.

But it will come at a hefty cost.

The labor-intensive commitment involves identifying those who have tested positive for COVID-19, the disease caused by the coronavirus, and interviewing them to find out where they have gone and whom they’ve come in contact with, an effort that has been effective in controlling other outbreaks, including tuberculosis and SARS.

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Before stay-at-home restrictions can be loosened and states and cities can begin the fragile process of emerging from isolation, public health experts warn that more people must be tested and then isolated through contact tracing to further diminish the virus's spread, while tracking who is healthy enough to go out.

A contact tracer is "a detective, investigator, in the public health space," Cuomo said during a news conference. "That is a massive undertaking ... an army of tracers."

But a recent report estimated that the high price tag for the implementation will require federal assistance.

Congress would need to appropriate about $3.6 billion in emergency funding for the effort, including for the hiring of 100,000 contact tracers, paid or volunteer, according to the report from the Johns Hopkins Bloomberg School of Public Health and the Association of State and Territorial Health Officials.

Crystal Watson, a senior scholar at the Johns Hopkins Center for Health Security and one of the lead authors of the report, told NBC News on Friday that public health departments of states and territories should be the ones determining how large of a contact tracing workforce will be needed and where it should be focused. And those states, such as New York and Massachusetts, with larger numbers of COVID-19 cases, will need to scale up accordingly.

Public health officials recognize that testing for the coronavirus has been woefully inadequate, and some public health experts have said that testing must be at least doubled or tripled from its current levels to allow for even a partial reopening of America's economy.

Watson said that those discussions for contact tracing need to happen and be implemented first before the reopening of the larger economy. But President Donald Trump has been pressing states with lower cases of the virus to reconsider reopening sooner, and on Thursday unveiled federal guidelines for "the next front in our war, which is called opening up America again."

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"I do think we need to buckle down. Right now, our attention is all over the place," Watson said. "If we put concerted effort into building [contact tracing] capacity for states, that is what allows us to transition to the next phase to reopen our economy. Without that, we're flying blind."

She added that the federal government's financial support will be essential, and that Washington lawmakers must act forcefully to ensure all states have the ability to launch their own tracing efforts, which will ultimately help break the chains of the virus' transmission in communities.

"It's a classic public health tool," Watson said. "But we don't yet have the scale of the workforce to do this on a national level."

Who will do the work?

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With some 22 million Americans now unemployed in the wake of the pandemic, the worst unemployment crisis since the Great Depression, the labor pool has ballooned. And the hiring of contact tracers can help some of those without jobs to "sustain themselves and give them a larger sense of purpose in all of this," Watson said.

Congressional lawmakers are now looking at how to fund the contact tracing efforts across the country, although the cost and how close they are to any definitive legislation or proposal remains unclear.

Evan Lukaske, a spokesman for Sen. Kirsten Gillibrand, D-N.Y., said she is working with colleagues to create a federally funded "care corps" that "local governments can direct to help do contact tracing, and help with many other urgent health needs during this crisis."

A time frame for the effort was not immediately known.

Meanwhile, Rep. Ami Bera, D-Calif., a former chief medical officer for Sacramento County, has suggested that the Trump administration establish a public health workforce of people from the Peace Corps or AmeriCorps.

"These individuals could also be used to enact widespread contact tracing or vaccine administration as we continue our efforts to defeat this virus," Bera said in a statement.

Dr. Keren Landman, a practicing physician, epidemiologist and journalist who writes about infectious diseases, was previously a contact tracer during a mumps outbreak in the Midwest and said it makes sense for a community to start tracing contacts in cases as a way to determine when members of society are no longer at risk.

"Let's say you're finding all of the cases are happening within nursing homes, and there's no implication that children are affected or can be affected," Landman said. "So you may want to think about reopening schools and day cares in some areas."

Collection of data is necessary for mitigation and tailoring each community's reopening efforts, she added.

"The alternative is going into a data-free zone and winging it," Landman said. "And winging it is going to cost us lives, and I don't think we want that."

Where has the effort started?

Massachusetts is at the forefront of implementing contact tracing, with Gov. Charlie Baker announcing that a public-private Community Tracing Collaborative will use 1,000 people to track down those with COVID-19. Efforts are already underway.

Massachusetts health officials said it will cost an estimated $44 million, including a mix of state and federal funding. The collaborative is in cooperation with the Boston-based nonprofit Partners in Health, which has tracked epidemics around the globe. Contact tracers will earn $27 per hour, the group said, although the state has begun using part-time volunteers as well.

The group has already received more than 2,000 applications. On Thursday, Baker asked residents to be responsive if they get a call from a contact tracer.

The effort, he said at a news conference, is "the key to stopping the spread of coronavirus and saving more lives. It will also be key to helping our state build a strategy for how we can get back to something like a new normal."

Contact tracing is a crucial piece of the necessary response to any pandemic, which is why we launched an innovative partnership with the team of experts @PIH.



This effort will help us collect more data to help slow the spread of COVID-19.#COVID19MA



🔗https://t.co/4zBXYiUSf7 pic.twitter.com/jOT6mzP8SF — Charlie Baker (@MassGovernor) April 14, 2020

A soft launch was rolled out in eight communities north of Boston, state Health and Human Services Secretary Marylou Sudders said. The preliminary results brought a surprise: While initial modeling predicted the typical person who tests positive would have 10 "very close" contacts, all of whom would have to be identified and traced, the actual number appears to be about six.

"So I guess that's good news," Sudders told reporters.

San Francisco, which along with other Bay Area communities moved quickly to implement stay-at-home orders in mid-March, announced an expanded tracing program this week. A growing number of volunteers — a cadre of medical students from the University of California, San Francisco, staff from the city attorney's office and librarians, among others — have been tapped to follow up with COVID-19 patients through a mobile app, text messages and phone calls.

Training of those volunteers has been occurring virtually via Zoom. The tracing is in conjunction with the opening of a new testing site in the city where people who may have been exposed can confirm if they have been infected, Dr. Grant Colfax, San Francisco's public health director, told reporters this week.

In Washington state, which had been an early hot spot for the virus in the U.S. but is no longer in the top 10 of cases in the country, contact tracing has begun in a handful of jurisdictions and partnerships with tech companies are a possibility down the line, said John Wiesman, the state secretary of health. A full cost for the effort in the state remains unknown.

Other states, including Pennsylvania, Rhode Island and Vermont, have reportedly begun discussions on contact tracing. A New York State Department of Health spokeswoman said the state is "actively working on a plan to greatly expand capacity" for contact tracing, but a cost amount was not immediately given.

Connecticut Gov. Ned Lamont said Friday on MSNBC that he's "certainly thinking about" contact tracing, but getting tech companies involved with collecting people's information may raise issues surrounding privacy and civil liberties.

Tech giants Apple and Google said last week they would form a partnership to build new tools that would enable people and health authorities to track the coronavirus using Bluetooth data from smartphones.

Watson said while shoe-leather investigating like in Massachusetts is essential for contact tracing, the use of technology to collect and transmit information can supplement human efforts. Digital contact tracing has been used by East Asian countries, which have seen the number of coronavirus cases fall in recent weeks.

Those who make public policy should start having conversations about data collection now so that people become more comfortable with the different forms of contact tracing, Watson added.

"What are we willing to accept in terms of these privacy issues and coordination to make sure that companies who want to work on this are not collecting and selling our private data?" she asked.

Ultimately, she said, contact tracing can't be done in a silo for each state to worry about on its own and the federal government needs to be an effective partner.

"This is needed everywhere — no state is exempt," she added. "If a state does not do this, if they do not make an effort to try and find and trace every contact, then they won't know whether the virus is in their communities, they won't be able to make an effort to stop the spread, and worst of all, they will see a spike in cases."