ALAMOSA — When looking at COVID updates from the Valley and beyond it can sometimes be easy to get lost in the numbers. As of Friday, the San Luis Valley had a 5.3 positivity rate, but what does that mean. And how can we apply it.
Positive tests divided by total tests equals positivity rate. So, if 100 people are tested in a week and 5 come back positive, that would be a 5% one-week positivity rate. Similarly, if 300 people get tested in a week and 15 come back positive, that would still be a 5% positivity rate. The larger the number of tests, the more confident officials can be that they are getting a fairly accurate picture of the level of virus circulating in the community. It is a metric of the presence of an infection in an area and a high rate could mean that only the sickest members of the population are being tested and there could be infected members of the community that aren’t being tested. Though it isn’t realistic to ask people who aren’t symptomatic to get tested strictly to get that number down. As such the positivity should not be considered alone.
Another important piece of data officials use is the one-week incidence rate. This is calculated by taking the total number of new cases in a week, and converting it into a rate per 100,000 based on population size. CDPHE shown a one-week incidence rate of 78.66/100,000 for the San Luis Valley as of Thursday. CDPHE’s data is a few days behind real-time, so when there is an increase locally in active cases, CDPHE will likely soon show an increase in local one-week incidence rate. Since they are measured weekly, incidence rates are used to see how often infections are taking place and then balanced for population using the 100,000 quantifiers to more evenly compare a less populated area to a more populated area for an ‘apples-to-apples’ view. Unfortunately, that means that lower population centers (below 100,000 total population) vary more greatly from week to week.
Public health officials look at both the positivity rate and the incidence rate together to get a good picture of the situation as it changes. To get up to date figures in the San Luis Valley be sure to visit https://www.slvphp.com/slv-regional-covid-dial/