How health experts track COVID despite underreported at-home tests
COLORADO SPRINGS, Colo. (KRDO) - As more and more Coloradans take at-home COVID-19 tests instead of traveling to a state-run testing site that tracks results, how will health officials know if there's a spike in cases or looming surge?
KRDO Newschannel Thirteen's Mallory Anderson talked with Dr. Rachel Herlihy, Colorado's State Epidemiologist about this topic and how they're tracking cases despite Coloradans underreporting cases.
Would you say the latest COVID case counts/reports are an accurate representation of how many cases are actually circulating in our communities or throughout Colorado?
Dr. Rachel Herlihy: So we know that underreporting is occurring and that has probably been occurring since the beginning of the pandemic when testing wasn't available necessarily. We know that a large number of individuals did not necessarily get tested. And then also one of the other challenges with COVID 19 is that a large proportion of individuals may have asymptomatic infections, and so they might not actually get tested. But you're completely right in that there is this proliferation of at-home testing that has occurred. That's obviously a really important tool for individuals to be able to quickly get that answer to whether or not they have a positive test result or not, but that does limit the number of results that are coming to public health.
What are the tools you use to track COVID cases outside of testing?
Dr. Herlihy: We're also looking at percent positivity. So of those results that are reported to public health and this is specifically those PCR tests, what proportion of them are positive? We can see that positivity value change as cases go up and down. We also track hospitalizations, and as severity levels have changed throughout the pandemic, having that severity data and hospitalization data has become increasingly more important to understand the full breadth of the pandemic and how it's impacting Coloradans. And then, of course, one of our new tools is wastewater data, and that is really much less dependent on individuals making choices to go get tested or have those results reported to public health. We have the ability to track that data over time without some of that dependence on individuals.
Are you also looking at the bigger picture, too, with case trends happening in the Northeast, what may be happening across the ocean in Europe?
Dr. Herlihy: Correct. We are certainly closely tracking what has happened in Europe as far as changes in what type of these Omicron subvariants are circulating. We're also watching South Africa right now where there are some subvariants, BA.4 and BA.5 that are emerging, and also closer to home. Looking at the East Coast of the U.S., we know that they are probably several weeks ahead of us in their second Omicron wave, this BA.2-driven wave. So we're closely watching that data, watching to see what their experience is going to be, trying to understand from them what sort of impact we might anticipate here in Colorado as far as overall burden of disease or cases and then also potential burden on our health care system.
If tests are being underreported due to at-home testing (or people having mild symptoms and not testing at all), how will we know if there is another surge?
Dr. Herlihy: One thing I would say that we are able to do with data is look at shorter-term trends. So while case numbers reported today might not mean the same thing as case numbers reported six months ago or a year ago, we certainly believe that the change in testing behavior, doesn't change overnight, right? So we can probably compare our case numbers today to case numbers a week ago, two weeks ago, three, four, six, several months ago. And that change in the number of cases is probably stable, meaning that we can look at an increase or a decrease that's occurring really over a short term to have a good sense if numbers are going up or down. Obviously the same thing with hospitalization numbers, we're closely watching hospitalization numbers to see if those are going up or down. And then also our wastewater data.
Are we worried that after the huge Omicron surge in the December, January, and February timeframe, that immunity is potentially waning as we head into the summer months and then into the fall?
Dr. Herlihy: That's actually a really good question and a question that we posed to our modeling team. There is a report available from the Colorado School of Public Health modeling team that looked at that question of are we going to see some sort of 'immunity cliff,' where suddenly we see this rapid drop off in the proportion of Coloradans that are immune and potentially could be at risk of infection. Basically, the answer is that we don't expect that to happen suddenly. There's really a lot of variability in individuals' duration of protection following a previous infection or following vaccination. So we don't expect suddenly one day to see immunity levels drop off. We know that immunity levels throughout the state continue to be quite high right now, both with vaccination having occurred in a large proportion of Coloradans, and then also that large Omicron wave that resulted in immunity through infection. We believe that we're still in a good place. The wild card continues to be whether or not we see a new variant emerge. And that's really what's going to change things, if we see a new variant emerge that has a high degree of immune escape, looks very different from variants that we're seeing right now. That is what could really be a challenge to us.
Originally when Colorado was mailing out COVID tests before the federal government decided to do it, there was a form that people could fill out to say whether or not they were positive or negative after taking that at-home test. Is that still something Public Health is doing and are you encouraging people to report their results?
Dr. Herlihy: I would say most important is for individuals to act on that positive test result. So that means making sure that they're isolating, letting their contacts know that those individuals who have been exposed may want to seek testing, watch for symptoms in themselves. But we are still very much interested in receiving those positive test results. There is still a place you can go on our website to report those positive test results to us, so certainly encourage individuals to do that.
Should the public have any fear that we could be caught off guard by the next surge?
Dr. Herlihy: We're watching trends closely, whether those are trends here at home, trends on the East Coast, or international trends, and trying to understand what that next challenge to us might be. We know that this virus has surprised us before, in the past. So we are certainly looking for any new challenges that might be coming our way and watching closely as we see the situation evolve globally.
Do you think at-home tests are being used more than in-person, state-run test facilities?
Dr. Herlihy: I don't have a great estimate of the volume of at-home testing compared to testing volume that's occurring in community testing sites. I think both are really important tools for Coloradans to use. We know that both can provide accurate results, and there's different use cases, I think, for some of the rapid at-home tests versus some of the community testing sites or clinic-based testing, or pharmacy-based testing that's available. I think, of course, one of the really important uses of those tests is for individuals that might be eligible for treatment. We know that it's important to have a positive test result early to go on to receive really the most benefit you can from treatment. So we encourage individuals that suspect they have been exposed or are feeling ill, to seek testing to really understand whether or not they might be eligible for treatment and be able to get that treatment as early as possible to have it be as effective as it could be.
What would you say the biggest takeaway should be for viewers on this topic?
Dr. Herlihy: We're seeing an increase in cases right now, and there is, unfortunately, going to be a number of Coloradans that are going to become infected over the next couple of weeks as we see this potential new surge in Omicron occur. So keeping in mind that those testing resources are still out there, whether those are community testing sites or at-home testing, taking advantage of those testing modalities that exist to really get access to treatment for those that are at highest risk and have that information to really protect yourself and your family. We also know that vaccines really continue to be the keyway for individuals to avoid severe infection. The data is very clear that individuals that have received vaccines, and especially those that have gone on to receive booster doses, are the population that is most protected against severe disease; so against hospitalization, and death.
Colorado's Department of Public Health and Environment says it has started to see an increase in cases statewide, as demonstrated via the case summary tab on the state’s COVID-19 data dashboard.
Colorado’s 7-day moving average of cases reported is 1,031, while 1,098 cases were reported Monday.
This data on the CDPHE website is updated Monday-Friday at 4 p.m. and includes data reported to CDPHE from the previous day.
Hospitalizations have also increased slightly, to 110 current hospitalizations.
CDPHE says this aligns with the recent modeling report’s projection that BA.2 and BA.2.12.1 may cause an increase in COVID-19 cases and hospitalizations in the next three months, though the peak is expected to be considerably lower than prior peaks.
The state health department believes the high levels of immunity in Colorado should help protect our state from a surge of severe illness.
