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Why are Dallas County’s COVID-19 numbers going down before the rest of the state’s? – The Dallas Morning News

Dallas County health officials have reported a downward trend of COVID-19 cases and deaths this month after a peak of at least 1,000 cases each day for more than two weeks in mid-July.

But Dallas County’s improvement isn’t being replicated across the state. As a whole, Texas has yet to experience a consistent decline in cases, and deaths are still on the rise statewide.

The seemingly conflicting numbers raise questions about whether both trends are possible as the number of Texans seeking COVID-19 tests drops and health experts stress people should continue wearing masks and social distancing.

Here’s what you need to know.

Why don’t Dallas’ trends match the rest of the state?

Health experts say it’s possible for some areas to improve during the COVID-19 pandemic, even if the overall state is not.

This is especially true in a state as massive as Texas, said Dr. Mark Casanova, president of the Dallas County Medical Society.

“Large urban areas are sort of affected disproportionately initially, and then you get spread into the outlying communities,” he said. “You certainly see that in North Texas … everybody across the state is on a slightly different clock.”

Health experts credit the local trend of fewer cases to compliance with social distancing and mask mandates, which went into effect in Dallas County in June, before the statewide order. Although the county saw a slight uptick in new cases this week after several weeks of lower numbers.

“We think that our community has responded well to the universal masking, the closing of the bars,” said Dr. Philip Huang, Dallas County’s health director.

Is Dallas really doing better?

Health experts say the decline in Dallas County’s cases appears to show what is really happening here with COVID-19 cases. If the number of cases was actually on the rise, the county would likely see a rise in hospitalizations. But, right now, that isn’t happening.

“Working with the modelers, looking at hospital data, looking at all these indicators, they’re consistent,” Huang said. “We are seeing definitely positive signs from that.”

Through Friday, Dallas County had an average this week of at least 497 daily cases. The county’s daily average of new cases fell to 463 last week, down from 654 cases the previous week and 827 the week before that.

Health experts acknowledge that across the state, changing testing technology, differing testing methods and rapidly evolving knowledge about the virus creates limitations to COVID-19 data.

In Dallas County, COVID-19 deaths and cases can vary significantly from day to day, largely due to reporting lags, raising questions about the reliability of current trends.

But health experts say a look at longer-term data gives a more clear picture of how the county is faring. Even with the ups and downs, overall the county is trending in the right direction: downward.

Since the virus can spread relatively quickly once someone becomes sick, seven-day averages are used to evaluate daily case trends, Casanova said. But hospitalizations and deaths should be evaluated using 14- or even 21-day averages, as serious cases of the illness can last weeks.

The county’s seven-day daily case average has declined since mid-July, while the 14-day average for deaths has slightly decreased since earlier this month.

That’s why the overall trends are said to be heading the in the right direction, even though there have been several days in recent weeks where the county reports deaths in the double-digits even as it reports fewer cases.

“A 50-year-old in a hospital undergoing intensive care, it’s not implausible that person was in the hospital for five, six weeks, sometimes even longer,” Casanova said.

Casanova said that when Dallas County had two weeks of at least 1,000 cases a day, people asked why there weren’t many deaths.

“Our comment was, regrettably, ‘Just wait,’” he said.

Slowing transmission in Dallas County

County health officials have also expressed cautious optimism about the local reproductive number, or the number of transmissions that result from each infection. A number below 1 means cases are going down. A number above 1 means cases are increasing.

At a news conference Thursday, County Judge Clay Jenkins said the current reproductive number is 0.87. Huang said that, based on data from Parkland Hospital, the reproductive number in the community has been below one since after July 4.

That’s slightly lower than some current estimates for the statewide reproductive number, which has been estimated this week to be about 1.2 by Statista and as high as 1.3 by the site Rt.live, which estimates reproductive numbers by state based on data from the COVID Tracking Project.

But Jenkins cautioned Thursday that the county’s reproductive number can easily change, and was even lower, at 0.68, 10 days earlier.

“All these numbers — hospitalizations, infections — move down slowly and up quickly,” Jenkins said. “But similar to the stock market, you can’t look at a one- or two- or three-day move, one direction or the other, and read much into it. You’ve got to look at it on a weekly and two-week basis.”

Positive test rate

Similarly, the county is generally faring better than the state when it comes to the positivity rates of COVID-19 tests. While a rate for all county testing sites is not available due to testing limitations, Jenkins said the rate was just under 16% for all the county’s hospitals.

Statewide, computer system changes had recently caused the number of total tests and the number of positive results to come in at different times, which inflated the proportion of tests counted as positive, state health department spokeswoman Lara Anton said.

For example, the state’s estimated average was at a record high of 24.5% on Thursday. But dipped down again the next day, to 16.1%. The state is working to reconcile the data and hopes to have the issue cleared up by next week.

But even a 16% rate is still much higher than the 5% positivity rate the federal Centers for Disease Control and Prevention has said indicates adequate testing, Jenkins said.

“If the positivity rate is high, it concerns you that the people that you’re testing are only the sickest people, and that you’re missing a lot of people,” Jenkins said.

Why are fewer people getting tested?

Huang has expressed reservations about the reliability of the positivity rate, since complete data for the number of tests run each day can be challenging to compile, both at the county and state levels.

But he said the improving situation in the county is also backed up by the lower demand for tests. The county said this week that there was a 40% decrease in requests for tests at the city and county sites, which haven’t reached testing capacity in several days.

“I don’t think it’s just that people are tired of tests,” Huang said. “I think that the masking is decreasing transmission and fewer people are symptomatic.”

Health experts: Keep taking precautions

Other health experts are concerned that the decreased demand for tests — a trend that has been seen at community test sites across the state recently — is due, in part, to a false sense of security that improving numbers might create.

Statewide, the seven-day average for COVID-19 cases fell from July 20 to Aug. 1 before jumping back up again, then declining again a few days later. Statewide deaths have not experienced any decline. Texas, as a whole, hasn’t seen the consistent downward trend Dallas County is experiencing.

Health experts said they fear that because the drop-off in tests coincides with an ebb and flow of cases, people will become less diligent about masking and following disease prevention guidelines.

In Dallas County, health experts caution that the downward trend does not mean the county is in the clear. Even with the decreasing number of cases, the overall numbers are still much higher than they were before the stay-at-home orders began to be lifted, Jenkins has said.

Casanova said while it is important to celebrate the positive trend, the data is strong evidence that residents need to continue prevention efforts like masks and social distancing.

“My ICU colleagues, my infectious-disease friends, we don’t control the public and individual decisions that are made on a whole to control [the outbreak],” Casanova said. “We’re in this together, but the public can make this happen. We’ll do our damnedest to save as many lives as possible, and do all that we can with as much as we can for as long as we can once they enter our hospitals. But so much of this is in the hands of the public.”

Staff writer Sue Ambrose contributed to this report.

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