Throughout the COVID-19 pandemic, the Health Department has kept thorough records about case transmission, number of people tested and the rate of positivity. As the projected growth of the disease has changed in the past month, the data reflects new challenges in testing, contact tracing and, ultimately, containing the spread.
The Boone County COVID-19 Information Hub tells one part of the story, and graphs provide a visual interpretation of changes over time.
Scott Clardy, the Columbia/Boone County Public Health and Human Services assistant director, answered questions recently about Boone County's numbers and what needs to be done to contain and mitigate the impact of the disease. Assume everyone around you may be positive, and act accordingly, he advises.
The soaring positivity rate
The positivity rate for a given time period is the number of positive tests divided by the total number of tests, times 100, Clardy explained. If the total number of tests goes down, then the rate goes up — an inverse relationship. And, as the number of positive tests goes up, the positivity rate also goes up — a direct relationship.
The national average number of positive COVID tests of the total administered is 5.5%, according to Johns Hopkins University. For Boone County, the seven-day average was most recently reported at 44.6%.
Clardy said the positivity rate in Boone County has been hit by a “double-whammy” recently — the number of tests has gone down, and positive cases have gone up.
The number of people getting tested has not expanded as the number of positive cases has increased.
Among the reasons for that: Health officials are prioritizing lab and testing resources for people of highest concern — for those with symptoms or who have been in close contact with a person who has tested positive. People need a doctor's note or an order from the Health Department to get tested. Several upcoming community testing events, however, will be free and won't require a referral.
With the influx of students at the end of August, lines at drive-through testing sites grew longer. Some people were not willing to wait in line, Clardy said.
The drive-thru testing sites in Columbia also serve more than just Boone County, he pointed out. Because Columbia labs are able to return results within 24-48 hours, testing here has become an attractive option for people from surrounding areas. However, results are reported to the county where the person lives.
Clardy said there are additional reasons people don't get tested in any communicable disease situation, mostly having to do with limited access: to transportation, information and medical insurance.
Because there have been more cases in the past 30 days and testing has not expanded to keep the overall rate constant, it's extremely probable that there are many more positive COVID-19 cases than have been detected.
“We are confident that there are more,” Clardy said.
Case numbers reported per day for the past 30 days show exponential growth. In other words, the total number of cases has doubled consistently, and will continue to do so if conditions for spreading the disease stay the same.
Clardy confirmed that the growth has been significant. The Health Department has taken steps to mitigate the exponential growth by ordering bars close by 10 p.m., and will continue to take additional steps as case numbers increase.
Besides case number daily totals, other important metrics contribute to the Health Department's decision-making about other possible mitigation measures. The health care system's capacity to handle an increase in cases, the availability of intensive care units, personal protective equipment, testing resources and ventilators as well as the Health Department's ability to investigate all play a role in determining next steps, Clardy said.
Standby: social distancing
The most effective way to slow the spread of COVID-19 involves full community effort. Clardy emphasized the dire necessity for everyone to social distance, wear masks and minimize contact. “Assume that everyone around you — including yourself — could be positive” and act accordingly, he said.
More people getting tested will also help identify cases, and provide more accurate statistics.
The Family Health Center is holding a free community testing event on Friday, Sept. 11. No doctor's note is needed. On Monday and Tuesday, the Health Department and the National Guard are sponsoring more free testing events, open to any resident of the state of Missouri.