The US's contact-tracing system is broken. Testing delays set it up for failure.

• Contact-tracing efforts in the US have been hampered by testing delays and staff shortages.
• As a result, many states missed their window to catch new coronavirus cases before outbreaks ballooned.
• The virus has now spread beyond the capacity of contact tracing, though public-health experts say it's still a useful tool.

An army of 100,000 contact tracers. That was the recommendation researchers at Johns Hopkins University came up with for the US in April.

"If we can find nearly every case, and trace the contacts of each case, it will be possible, in time, to relax the bluntest approaches: the extreme social distancing measures, such as stay at home orders," they wrote in a report.

But no army of investigators ever came to fruition. An NPR analysis found that the US had only commissioned around 37,000 contact tracers as of June, and only seven states had enough tracers to contain their outbreaks by that point. Most states relaxed stay-at-home orders without that infrastructure in place.

"The ideal situation with contact tracing is you find every case and you chase down every contact, and then you provide support so that people can isolate or quarantine, and then you stop the virus in its tracks," Dr. Carolyn Cannuscio, a social epidemiologist who leads the contact-tracing program at the University of Pennsylvania, told Business Insider. "That would be a dream. That's what we all wish for. That's not the situation we're in now."

In addition to the US's slow and insufficient hiring of contact tracers, the tracing efforts that have been implemented so far are hampered by testing delays. A slow turnaround for results makes it difficult to identify cases while a person is still infectious.

"There are cases in which we reach out to contacts to let them know about their exposures, but they're already hospitalized because of the testing delays," Cannuscio said.

Meanwhile, the US's case counts have swelled to levels that make contact tracing nearly impossible. When the Johns Hopkins researchers released their report, the US had confirmed nearly 500,000 infections. Now the total has exceeded 4.8 million. The country's seven-day average of new cases sits well above 50,000 per day.

"So many other parts of the system are broken that it can feel very dispiriting to contact-tracing teams," Cannuscio said.

Testing delays can nullify contact tracing

Epidemiologists suggested a three-step strategy to contain the virus in April: test, trace, isolate.

But those steps must go in order, and the US's public-health system failed to deliver on the first one.

The CDC was at first slow to distribute tests, then it sent out faulty tests in February. As a result, lingering shortages of accurate tests meant that only patients with severe symptoms were eligible. This was compounded by the fact that many people didn't know their symptoms were coronavirus-related in the first place, since the CDC initially listed only three COVID-19 symptoms: a fever, dry cough, and shortness of breath.

US testing has since ramped up considerably. As of Wednesday, the US was administering 174 tests for every 100,000 people per day, putting it second in the world behind Hong Kong in testing per capita. In total, the US has administered more than 58 million coronavirus tests.

But delays and shortages are still a problem.

The nation's weekly average number of tests fell by nearly 8% from July 29 to August 4, according to data from Pantheon Macroeconomics. Testing per capita also declined in at least six states — Alabama, Florida, Iowa, Kansas, Utah, and Washington — over the last two weeks.

Across the country, people are waiting weeks to get test results, since companies like LabCorp and Quest are struggling to keep up given the rapid spread of the virus.

"We have a broken testing system, and that sets us up for failure in contact tracing because people are waiting so long to get their test results that we have missed a critical period for counseling those people to stay home and avoid infecting others," Cannuscio said. "We've also missed a critical period for identifying all the other people they may have come into contact with during their infectious period."

For those reasons, she said, testing delays can sometimes render contact tracing useless: "If any part of the system is broken, then the whole system fails."

Contract tracing has a follow-up problem

Even with perfect testing, contact tracing isn't flawless. Some infected people may not want to disclose information about their contacts, especially if those people are undocumented. Others may have difficulty remembering who they saw over the last several days. And plenty might not answer at all.

"If we think about the current climate of endless spam calls to people's cell phones, it's easy to understand why people might not pick up the phone, especially if it's an unfamiliar phone number calling," Cannuscio said.

Contact tracers in South Florida are connecting with less than 20% of the people to whom they reach out, according to a letter from Miami Beach Mayor Dan Gelbert. And just 42% of coronavirus patients who spoke with a contact tracer in New York City provided the name of another person they may have infected, the New York Times reported last week.

Cannuscio said her department, which works with the Philadelphia Department of Public Health, reaches about 80% of the people who test positive within their health system. But the bigger issue for contact-tracing teams, she added, is a lack of follow-up after cases have been identified: Contact tracers don't always have time to make sure sick patients get the care they need, including food and hygiene products, so those individuals may still leave their homes to get basic necessities. Some infected patients may also require help accessing resources like unemployment or disability insurance.

"We've done a very poor job of providing support for people to quarantine so that they can maintain their basic material needs for themselves and their families," Cannuscio said. "We need to incentivize people to stay home."

The US outbreak is now too big to trace

The Department of Health and Human Services provided $11 billion for states to expand testing, surveillance, and contact tracing efforts in May. But many contact-tracing teams still remain short-staffed, either due to funding shortages or a lack of political will to augment these workforces.

Now, some public-health experts argue, the window in which contact tracing would have made a difference has passed. The tool is most effective at the start of an outbreak, when cases are relatively low. Once the virus really starts to spread, it's like wildfire: A single case can turn into more than 59,000 after just 10 rounds of infections, according to the Johns Hopkins report.

"Contact tracing is the wrong tool for the wrong job at the wrong time," Dr. David Lakey, the former state health commissioner of Texas, told the New York Times on Friday.

But Cannuscio said contact tracing can still curb local outbreaks.

"Every case is somebody's sister or brother or child or grandparent or parent," she said. "If we have these teams in place, why wouldn't we try to aggressively intervene to provide support, to provide help, and to maybe delay or prevent a new case?"

Plus, contact tracing may become more valuable again once cases decline.

"We're all tired, but the sense of urgency hasn't waned," Cannuscio said. "It's still critically important to intervene and to intervene quickly."