Medical leaders not clear why COVID-19 positivity rate climbing in Texas

HOUSTON – Medical experts have no clear answers as to what is driving an increase in the positivity rate for COVID-19 in Texas.

The rate, which represents the percentage of people testing positive for the virus, is derived from the number of new coronavirus cases reported to the state each day, divided by the number of positive viral tests reported each day and averaged out over a seven day period.

What is the rate in Texas?

According to the Department of State Health Services, the positivity rate Friday was 16.79 percent in Texas. That number is just shy of the state’s mid-June high of 17.43 percent.

The positivity rate was steadily declining from that point but again started to climb at the beginning of August.

Hospital rate not keeping pace

While the positivity rate continues to climb, the state’s hospitalization and ICU rates remain flat, even declining.

However, Dr. James McDeavitt, the dean of clinical affairs at Baylor College of Medicine, cautions the public not to make decisions based on hospital rates.

“Hospitals are ok. That is great. It’s important, but we really have to drive that community incident rate down,” said McDeavitt. “We can’t keep skating up to health system collapse as our societal metric. We have to get control of this in the long term.”

Dr. Sheri Onyiego, the head of nutrition and chronic disease prevention for Harris County Public Health, also said hospitalization rates can change.a

“Keep in mind not everyone that’s positive doesn’t necessarily mean they go to the hospital,” said Onyiego. “There is a lag between someone having a positive (test) today and then becoming sick and then being sick enough to go to the hospital.”

Difficult Data

McDeavitt said answering questions like this can be difficult given how data is collected.

“We got city data. We got county data. We got state data. We got individual counties contributing data,” said McDeavitt. “It’s not always apples-to-apples and it’s in different systems. It’s not easy to answer some questions you would think it would be easy to answer.”

State health officials tell KPRC 2 this is the first time it has ever collected data on this scale. Yes, the state has long kept data on other diseases like measles, pertussis or flu, but COVID is different.

State health officials said this is the first time Texas has gathered both positive and negative test results for viral and antibody tests. With other diseases, the state only recorded positive tests.

State officials also said there can be a lag as to when test results are reported, which can impact percentages.

Theories Abound

There are several theories behind this recent increase in numbers. One is more asymptomatic people are testing positive, along with younger people, who can weather the virus without going to the hospital.

McDeavitt said the increase may also be due to a lag in test results finally coming in.

“I think what we might be seeing now of lab results coming into the system that were actually people who were tested two or three weeks ago,” said McDeavitt.

Adding a confusing wrinkle to the increase is what state health officials said is a decrease in the daily number of test results.

State officials said the number of daily cases being reported is also decreasing, but not as much as viral test results. State officials said a smaller number of test results can also throw off the percentages.

State officials aren’t sure whether this is what is driving an increase in the positivity rate and they are also not yet sure whether fewer people are getting tested or if there is a bottleneck in their system.

About the only clear answer from the medical community is that the virus is still very much prevalent in our community and while thousands of new cases are being reported every day, now is not the time to relax.