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Why the Low Coronavirus Positivity Rate in New Mexico Remains

The state is performing much better than its neighbors on a key coronavirus metric called the test positivity rate, which measures how many people who get COVID-19 tests turn out to have the disease.

by Jens Gould, The Santa Fe New Mexican / August 10, 2020

(TNS) - Last month in Arizona, a staggering 1 in 4 people tested for COVID-19 received a positive result. 

Currently in Texas, it’s about 1 in 6.
Yet in New Mexico, the numbers are very different. About 1 in 30 tests is coming back positive.
The state is performing much better than its neighbors on a key coronavirus metric called the test positivity rate, which measures how many people who get COVID-19 tests turn out to have the disease.
The statistic is an indication that New Mexico is proving itself to be a safer island — epidemiologically speaking — in a sea of states doing a poorer job of monitoring and controlling the virus.
It also helps explain why officials were able to report a steep decline in the state’s COVID-19 transmission rate Thursday, just several weeks after New Mexico experienced a troubling surge.
“We’ve had a couple of peaks, and hopefully we’re through a big part of the second peak,” said state Human Services Secretary David Scrase, a main figure leading the state’s efforts against the novel coronavirus.
Test positivity rates are gaining more visibility nationwide as health officials look to them as a key factor in making decisions on reopening the economy. Unlike the rate of new cases or hospitalizations, the positivity metric helps determine whether testing is widespread enough to accurately understand the spread of the virus.
And among the dizzying trove of COVID-19 statistics being analyzed in New Mexico, this number is taking more prominence: State officials just added it to the list of criteria they use to make policy decisions about reopening the economy, which has taken a severe hit through the crisis.
While Gov. Michelle Lujan Grisham has said it’s been difficult to watch the economic hardship, she’s reiterated that her public health mandates have been necessary.
She recently noted members of the state’s Economic Recovery Council had questioned whether adding the test positivity rate to the state’s gating criteria would be “moving the goal posts” on the metrics used to decide how and when to reopen the economy.
But the governor and Scrase have dismissed that notion, saying including the statistic helps them make better policy decisions. Scrase likened its addition to the greater assortment of professional baseball statistics now available to fans compared to what existed years ago.
“You have a better sense of what this player might be able to deliver,” he said in an interview.
“I don’t think we’re making any taller hoops or anything else,” Scrase added. “We’re just doing everything we can to understand the epidemic better and make sure the next time we do some reopening, we don’t get the same result we did when we did it in early June.”
Fractions and math
To understand the test positivity rate, Scrase explained, it’s helpful to think of a fraction in mathematics.
The top number, known as the numerator, is the total of COVID-19 cases detected over a given period of time. The bottom portion in the fraction, or the denominator, is the total number of tests conducted during that period.
Now divide the numerator by the denominator. In New Mexico, you get a seven-day rolling average of 3 percent through Aug. 6, according to state figures. Johns Hopkins University data puts the rate even lower for the state, at 2.6 percent.
That’s a far cry from Arizona and Texas, where that number is now around 16 percent for both states, according to Johns Hopkins. Utah and Colorado are faring better, but still well above New Mexico. That’s also true for the entire U.S., at 7.5 percent.
The meaning of the math, officials said, is twofold: New Mexico is doing a better job at controlling the spread of the virus than many states while at the same time testing more people per capita.
“A low positive rate, when you’re doing adequate testing, is a good indicator that the community is doing well,” said Dr. Jason Mitchell, chief medical officer for Presbyterian Healthcare Services and a member of the state’s Medical Advisory Team, a key unit in dealing with the state’s COVID-19 response. “And a high positive rate is a very dangerous indicator.
“So, when you look at other states in the U.S. and they have a 16 [percent] or 20 percent positive test rate, that means there’s a lot of spread you may or may not be aware of,” Mitchell added. “That’s a scary number to have.”
As for New Mexico’s numerator, Scrase said many residents’ compliance with social-distancing and mask-wearing instructions has helped keep the number of cases down. A few weeks ago, during a resurgence of the virus that saw the test positivity rate briefly rise above the state’s 5 percent target, the governor and her administration admonished residents for being too lax in adhering to those orders.
But things have changed, Scrase said.
“The people of New Mexico have been cooperative with us and adapted, and I think mask-wearing is way better than it was even a month ago,” Scrase said.
The reopening debate
State officials, who have been heavily criticized by some for going slow in reopening the economy, insist health restrictions have been critical to the improvement. New Mexico shut down its economy sooner than most states when the pandemic first hit, and it didn’t go as far as some others when it began to reopen in June.
Texas, by contrast, reopened sooner and had one of the shortest initial stay-at-home orders in the country. It also let bars open before shutting them down again.
Additionally, while New Mexico reinstated a ban on indoor dining at restaurants after cases resurged in July, Texas has kept such service partially open.
“If you’re going to pull a Texas and reopen bars, that’s going to be a big problem,” said Kathryn Hanley, a biology professor at New Mexico State University who specializes in virus evolutionary ecology. “People acted like there had never been a pandemic.”
New Mexico’s contact tracing efforts also are helping to keep the spread down, Scrase said, as Health Department tracers are reaching over 80 percent of people who test positive.
Contact tracing is a disease-control strategy used to track people who have been in close contact with carriers of the coronavirus so they can be isolated and officials can limit the spread of the virus.
All of these factors combined have led to the recent sharp decline in the state’s COVID-19 transmission rate, officials said. The spread rate dropped to 0.72 as of Thursday, a level well below the state’s target of 1.05 and an indication the number of infections is now on the decline.
As for testing — the denominator in the test positivity fraction — New Mexico has significantly ramped up its capabilities over the past few months, increasing from around 4,600 tests per day in mid-June to around 7,900 per day by late July.
Several factors have helped the state achieve that broader capacity, including the fact that around four-fifths of all tests are processed at two labs — TriCore Reference Laboratories and the state’s own facility.
Those buildings are located near each other in Albuquerque, Scrase said, helping the state cut down on turnaround time for results and any hiccups that can arise because of lengthy transportation times.
It also has helped that the state Department of Health has repurposed much of its workforce to run testing operations and experts from private health care providers advised the state to use the best testing equipment, Scrase said.
“We’ve stuck to those tests that are most accurate,” he said.
Several of the state’s leading health care providers recently announced they no longer would administer tests for asymptomatic people amid a temporary disruption in accessing testing supplies. But that decision does not appear to have stopped overall testing numbers from going up.
“There is, at this point, enough capacity at different institutions that are taking up the slack to test asymptomatic people,” Hanley said.
Magnets for criticism
Not everyone is happy with the state’s efforts to fight COVID-19, even if they do mean better metrics than neighboring states. State Republican leaders have criticized the governor over her emergency orders, arguing Lujan Grisham has gone too far and is causing irreparable economic damage.
“While we welcome the news that infection rates are going down in New Mexico, the damage has been done: thousands of lost jobs, a shattered economy, closed businesses, a state budget drowning in red ink,” state Republican Party Chairman Steve Pearce said Thursday. “These are the true vestiges of the governor’s poor leadership.”
Some New Mexico business owners are irate as well. Several filed a lawsuit against the governor that argued her enforcement of the mandates was unlawful, but the state Supreme Court ruled against them last week.
Still, the economic harm of the pandemic and the state-ordered shutdowns is palpable. New Mexico’s economy might have contracted nearly 30 percent in the second quarter, according to a Moody’s Analytics forecast cited by a leading state economist Friday.
Dawn Iglesias, chief economist at the Legislative Finance Committee, also cited a report by the company Yelp, which found 687 businesses have closed in New Mexico since the start of the health emergency. Of those, 355 were permanent closures, Yelp’s report said.
As the news swings from good to bad and back, the greatest question facing state officials and medical advisers charged with managing the pandemic response remains the same: Will eventual steps to reopen the economy again drive up the test positivity rate and the transmission of COVID-19 in New Mexico?
Not if New Mexicans wear masks and maintain social distancing, said Mitchell, of Presbyterian Healthcare Services and the state’s Medical Advisory Team.
“It is not futile. It is not hopeless,” he said. “If we follow the basics, then we have a lot of hope and we’ll continue to be a successful state.”
©2020 The Santa Fe New Mexican (Santa Fe, N.M.)
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