As The D.C. Region Reopens, Some Question The Area's High COVID-19 Positivity Rate The Washington region has particularly struggled with this measure.
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NPR logo As The D.C. Region Reopens, Some Question The Area's High COVID-19 Positivity Rate

As The D.C. Region Reopens, Some Question The Area's High COVID-19 Positivity Rate

A nurse tests a patient for COVID-19 at the Neighborhood Health clinic in Fairfax County on May 5. Daniella Cheslow/WAMU hide caption

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Daniella Cheslow/WAMU

As the Washington region moves into its first phase of reopening — D.C. and Northern Virginia on Friday, Montgomery and Prince George's counties next week — many people might rightfully be asking: are we really ready for this?

Local officials say yes, pointing to metrics that largely show declining COVID-19 case counts and hospital systems that are prepared to handle any future surge of infections. But one number that seems to have been set aside is the positivity rate — the proportion of people who test positive out of the overall number of people tested.

The higher the positivity rate, the worse things are generally thought to be. The World Health Organization says countries, states and cities should aim for a positivity rate lower than 10%, and less than 5% would be ideal. On that latter measure, a majority of states are falling short, according data tracked by Johns Hopkins University.

The Washington region has particularly struggled with this measure. Just last week Dr. Deborah Birx, the White House's coronavirus response coordinator, said that D.C., Maryland and Virginia have the highest rates of positive tests in the country. As of this week, the positivity rate in Northern Virginia hovered around the 20% mark, while it stood at 14.4% in Montgomery County and 19.4% in Prince George's County. In D.C., the positivity rate was 17.2% last week, far above what city officials said in late April would be ideal for a first phase of reopening: a sustained decrease for 14 days and reaching 5%.

So what gives? Are local leaders moving the goalposts in a rush towards reopening? Or have conditions on the ground changed, making them comfortable with a limited reopening even as the positivity rate remains above ideal thresholds?

"I think making some decisions and then scrutinizing the data afterwards to see what happens and be willing to course-correct is an OK approach," says Dr. Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security. "That said, we can't wholesale discount indicators that are too hard to fix or aren't looking in our favor, because we will be surprised."

What The Positivity Rate Tells Us

Experts say the first thing to consider is that the positivity rate is largely a reflection of testing. The more testing for COVID-19 that gets done, the lower the rate should fall.

Much of the testing in and around D.C. since mid-March has been limited to people likely to be infected: first it was just for people with a history of international travel and symptoms, then it expanded to at-risk groups, and it has been growing since. But it's still not broadly universal.

"If you have a high number like we have currently in D.C., it just shows that really people who are the sickest, who are showing up for care are the people who are getting tested and diagnosed. It shows us that we're really don't have a great grasp of what's happening in the community as a whole," says Dr. Anne Monroe, a professor of epidemiology at the George Washington University's Milken Institute School of Public Health.

That is changing, though. Next week, D.C. is opening a third public testing site, and there have been a number of pop-up testing events in hard-hit neighborhoods. Mayor Muriel Bowser said this week that testing capacity across all labs and clinics in the city is now at 5,500 tests a day.

The governors in Virginia and Maryland have also both said that testing capacity is ticking upward, with Virginia Gov. Ralph Northam noting that CVS is opening 39 drive-thru testing sites, including 12 in Northern Virginia.

"We want to encourage people to come out and get tested so we can really get a good sense and catch cases early so that people can be isolated and not spread it to others," Monroe says. "But it's a very different message from the message we had as recently as a month ago. And I think that's a real challenge and something that's going to have to be overcome."

And it's a message that Bowser echoed this week, when she announced the details of the first phase of reopening. "If you need a test, get a test," she said.

Overall, while the positivity rate generally remains high across the Washington region, it has been trending downward.

On Thursday, Hogan said in Maryland it had fallen to 12.4%, less than half what it was in mid-April. By Friday, it was at 12%. In hard-hit Prince George's County, the positivity rate declined from 30% two weeks ago to 19% last week.

Data show general declines also in D.C. and Virginia, but both jurisdictions also remain above the 10% threshold.

Managing The Risk

Dr. Hongjie Liu, the chair of the Department of Epidemiology and Biostatistics at the University of Maryland, says anything above a 10% positivity rate shows there's certainly still an epidemic.

"For any infectious disease, these levels of positivity are extremely high, indicating in our society there are a lot of infected cases that can transit the virus to others," he says.

Nuzzo agrees. "That suggests that there are other infections out there that they're just missing and not counting them, not seeming to be able to intervene and stop them from spreading," she says.

But Liu also approaches the situation in a pragmatic way, saying that a higher-than-ideal positivity rate and a limited reopening can coexist.

"If we can take personal protections, we still can reduce the risk for infections. For example, wear a mask in public, wash our hands and keep six feet distance," he says. "If you eat lunch or breakfast or dinner in a restaurant, the risk is very high. However if you move all those tables outside, the chance for us to be infected will be largely reduced based on recent studies."

And that's what's happening across the region: while restaurants may be reopening, only outdoor and socially distant dining in small groups will be allowed. And while retailers will be able to offer curbside service, many other businesses — like gyms and spas — will remain shuttered. Parks will open, but playgrounds will largely stay off limits. Northam also said masks would be required across the commonwealth starting Friday.

Bowser stressed that a first phase of reopening should not mean people assume life has returned to normal.

"As we begin reopening... every single one of us has a role to play. It's critical that people wear masks, social distance and practice good hygiene," she said. "We have a shared responsibility to stop the spread of the virus."

Liu adds that testing and contact tracing capabilities have to continue to increase in D.C., Maryland and Virginia, and aggressive steps have to be taken to isolate positive cases as soon as they are found.

Monroe agrees that the risks are generally limited in the first phase of reopening. And she says that the changing emphasis on the positivity rate is, in part, a factor of how local leaders and health officials are learning about the virus as they go — and balancing a number of variables in deciding when to reopen.

"Initially test positivity was floated as a metric that would be used to determine re-opening. And it's not currently being used. It doesn't mean that it's being completely ignored and it wouldn't be factored into future decision making. I think that the leadership in D.C. has been thoughtful about the metrics that they've chosen," she says.

Still, leaders in D.C. did make a shift in their own thinking on an acceptable positivity rate. While officials said in late April that 5% would be an ideal threshold, they more recently said they'd be fine with anything under 20% and ultimately dropped the positivity rate as a metric for reopening. (They have four others: the number of COVID-19 cases, hospital capacity, testing, and contact tracing.)

"Everything about this pandemic changes every single day," says Monroe. "And so I think that local leaders have been thoughtful and responsible with information that is just constantly changing. And that's really, really hard."

Still, Nuzzo says she believes that the positivity rate is a valuable metric to follow — and even if leaders in the Washington region are now looking beyond it, they'll still have to keep an eye on it as reopening progresses.

"If I were a governor or a mayor, what I would be scrutinizing is the positivity rate once I begin the process of opening, because if that starts to tick up, then that suggests that we may have a problem and a course correction is necessary to further expand testing to make sure that we are capturing all of the new infections that are going to occur with the reopening," she says.

Monroe agrees that testing will have to continue ramping up across the Washington region to continue spurring the declines in the positivity rates that most health officials want to see. "That's going to help us continue to get where we need to go," she says.

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