The updated data the public sees each day about the number of COVID-19 cases in Arizona reflects the spread of the disease as it stood a week ago or longer because of delays that take place in obtaining results.

In addition, it only reflects part of the spread because of limited test availability and restrictions on who can receive a test.

The result is an incomplete picture of how things once stood with the disease, not how the situation actually is today.

It takes a person about five days on average, though it can be up to two weeks, to show symptoms after being exposed to the virus. Because testing is limited to those who are very ill or high-risk, it can take another few days or a week to become sick enough to get tested.

From there, if you’re able to get a test, it can take a few days to a week before you get the results. Those results are then reported to the state and counties. The numbers then start to appear on public case counts.

“What you're seeing is what happened a few weeks ago,” said Dr. Bob England, Pima County’s health director. “So we are behind the curve. We are always going to be behind the curve in terms of where transmission is happening now. And that's something to keep in mind when people talk about relaxing some of the social mitigation that's been put into place: You're looking at where you were weeks ago.”

And, even once the results are reported publicly, they’re incomplete. The case numbers don’t account for those who are infected but couldn’t get a test or stayed home and didn’t seek care in the first place, he said.

“There's a lot to be desired,” England said.

Jessica Rigler, assistant director of the Arizona Department of Health Services, said the state typically expects a four to seven day lag in the data because of the turnaround time for testing.

Counties receive the data as soon as the state gets it because they share a surveillance system, she said.

"The data that gets posted is really a look back on what has happened in the state in the last week or two, not what's happening today," Rigler said.

Delays in results at the county level

Maricopa County’s coronavirus reporting cautions the public to recognize this lag in data when assessing case numbers.

“This number is likely to increase as there is an 8 day reporting delay from when specimens were collected,” the county’s report, updated daily with information on cases, says.

Dr. Rebecca Sunenshine, Maricopa County’s medical director of public health, said eight days is the longest the process could take from test collection to public reporting.

She said the timing depends on which laboratory is being used and where its processing lab is located. Depending on the lab, she said, specimens are sent to California or sometimes even across the country to be processed, adding to the delay in results.

The private lab then processes the results, which can take a few days. They then are reported electronically to the state. The county then accesses that information and publishes it in daily Maricopa County updates.

The state laboratory is typically faster, Sunenshine said, but relatively few tests are processed there. Of the 3,962 confirmed positive cases reported by state health officials Wednesday, just 203 were confirmed by the state lab.

“It’s a bit complicated, but that’s why it can take up to eight days, but sometimes we have those results as soon as a few days,” Sunenshine said.

In Coconino County, which currently has the fourth-highest case count among Arizona's 15 counties, public health officials understand there’s both a test shortage and results lag, so testing results do not affect their response, County Epidemiologist Matthew Maurer said.

“Knowing that we have an insufficient supply of collection specimen kits and materials for collecting specimens, we’re having to treat people that are sick and experience symptoms of COVID-19 all the same,” Maurer said. “Regardless of whether you’re able to get tested or not, our interventions are still the same.”

Maurer said compared to the early days of coronavirus, test reporting speed has improved significantly. On average, the county receives results reported to the state about four days from the test date. The range from a day or two to up to eight days depends on where the test is collected and where it’s sent for processing.

Results can take anywhere from two days to 12 days, England has seen in Pima County.

How labs share result information

Initially, the two main private testing companies, Sonora Quest and LabCorp, had to send the tests out of state to be completed, England said. By March 20, Sonora Quest had begun processing tests in Tempe, where all swab samples handled by the company are tested.

Labs send a list of positive tests to the state electronically each day, England said. But many times, the database includes only a person’s name and the provider or facility that ordered the test, he said. The county then has to follow up with the provider to get contact information for the person who tested positive, he said. They don’t usually get a phone number or address.

"That sometimes can result in delays before we can get to the bottom of it, find out anything about the person, talk to their household contacts, make sure everybody knows what they need to be doing, and so forth," he said.

Sonora Quest so far has reported more than 27,000 test results to the state health department. Their average turnaround time for test processing at the Tempe site is 36 hours. This means on average, it takes a day and a half for the physician to learn the test result after the lab receives the specimen, according to Brian Koeneman, Sonora Quest’s scientific medical director.

Sonora Quest sends all their test results to the state once a day. It’s then in the state’s hands to sort out and display the results publicly. It’s unclear how long that process takes. Koeneman said eight days seems on the long side.

“I don’t know where that sample is going to for an eight-day turnaround time," Koeneman said. "But if they’re backlogged, it could take a couple days for them to get to the test, actually getting to that sample," he said of other labs.

As far as Sonora Quest, Koeneman said he’s not aware of any testing lag. As soon as the lab finds results, they’re sent to the ordering physician and the state system.

Shortage of test supplies, knowledge

Koeneman said there remains a shortage of test swabs and collection devices needed to meet patients’ and providers’ demand for tests.

Problems that are causing delays or affecting the response to the virus, like the lack of enough plastic swabs to get samples, have surprised England in Pima County.

“It’s astounding to me that we can't even, this far into it, produce enough personal protective equipment and test swabs. I just … it's mind boggling. But that’s where we’re at,” he said.

Policymakers who will decide when social distancing orders can be relaxed need good information first, England said.

Any speculation about whether these orders can be lifted by a specific date is the wrong way to look at the issue, he said.

Instead, England said, certain measures need to implemented first: There needs to be abundant testing for anyone who wants or needs it, a solid understanding that we’re well past the peak of cases, a health care system with adequate resources and a public health system that can rely on testing well enough to conduct investigations and do contact tracing to cut off transmissions.

"If we get all those things in place, then we can start relaxing some of the social mitigation one step at a time and see what happens," he said. "But that ain't happening by the end of the month."

Reach the reporter at Alison.Steinbach@arizonarepublic.com or at 602-444-4282. Follow her on Twitter @alisteinbach. Reach reporter Rachel Leingang by email at rachel.leingang@gannett.com or by phone at 602-444-8157, or find her on Twitter and Facebook.

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