» Study: Houston could see virus cases spike in June.
Health model uses cellphone data to track social distancing
Houston is one of several cities in the South that could see spikes in COVID-19 cases over the next four weeks as restrictions are eased, according to new research that uses cellphone data to track how well people are social distancing.
The updated projection, from PolicyLab at Children’s Hospital of Philadelphia, found that traffic to non-essential businesses has jumped especially in Texas and Florida, which have moved aggressively to reopen.
In Harris County, the model predicts the outbreak will grow from about 200 new cases per day to more than 2,000 over the next month.
“Some areas — particularly in the South — that have moved more quickly to reopen are showing a higher risk for resurgence,” the researchers wrote in a blog post. “If people in Houston and Palm Beach, Fla., for example, aren’t being cautious with masking in indoor crowded locations and with hygiene and disinfection, local governments may need to intervene again should they lose control of the epidemic.”
Bexar County, which includes San Antonio, will also see an increase in COVID-19 cases according to the projection, but would still be below 100 new cases per day. Bexar reported 44 new cases on Wednesday, a Hearst Newspapers data analysis shows.
And in North Texas, UT Southwestern Medical Center found in a study last week that Dallas County could see 800 new cases a day — about three times what it’s seeing now — by late June if restrictions are relaxed.
Scientists from across the country have been warning for some time of a possible “second wave” of COVID-19 this fall, but few have pointed to a timeline as early as June.
One epidemiologist interviewed by Hearst Newspapers cautioned that modeling is not a perfect science because of the limitations of the data — it takes time for a person to develop symptoms, get tested, and get results.
Of course, scientists also of course can’t predict how policy choices will play out and how people will react to them.
Texas has been doing well by some measures as it reopens — hospitalizations are mostly steady and the rate of people testing positive for COVID-19 has fallen as access to testing expands. The state reported about 26,000 tests per
day over the past week, nearing Republican Gov. Greg Abbott’s goal of 30,000.
But daily new cases remain at their highest point since the outbreak began in March. Outbreaks are especially hitting El Paso and meatpacking plants in the Panhandle. Abbott has sent in “surge response teams” to help contain local outbreaks, but as more of the state reopens, public health officials worry that infections will spread too quickly.
Abbott has said all along that he expected the number of Texans testing positive for COVID-19 to increase as the state’s ability to test improved. But as he reopens the state, he’s said he’s focused on the state’s declining positivity and hospitalization rates.
“All the trends are going good in Texas,” Abbott said during a Monday interview on Fox News.
The PolicyLab research is tracking 389 large counties across the country with active outbreaks. It found that projections are best in places that are relaxing restrictions selectively in areas with fewer cases and less transmission.
“Given these cautious actions by our governments, we have already seen that the predicted resurgence has not occurred in most places that are beginning to reopen — rather, daily cases are either plateauing or falling,” the researchers wrote. “But the picture our models are painting for Texas and Florida provide ample evidence to others who would choose to move too quickly. We see these concerns even as we adjust for additional testing capacity that might have inflated our forecasts.”
Several research institutions across the country have models for forecasting COVID-19 deaths, and in general they show that states tallying large numbers of deaths are more likely to see substantial rises in fatalities in the future.
One of those models comes from the University of Texas at Austin, where Lauren Ancel Meyers, who leads the school’s COVID-19 Modeling Consortium, said whether cases and deaths increase in the weeks ahead depends on whether people take the recommended precautions.
“The cellphone mobility data clearly shows that people are leaving their homes for more of the day and going to public places like parks, grocery stores, and restaurants more often,” Meyers said in an email interview. “If most people are being cautious — wearing face coverings, keeping physical distance, and staying home if they have even mild symptoms — then we may not see an immediate spike in transmission.”
Meyers said it’s difficult to speculate about a resurgence in June, or even fall as has been predicted by other epidemiologists, because there’s a significant lag in the data. Deaths often occur three or more weeks after an infection, and it’s yet to be seen how reopenings will go.
“Our forecasts only go three weeks into the future because we cannot predict policy and behavior,” Meyers said. “As policies are relaxed, the choices people make and our capacity for COVID-19 testing, contact tracing and isolation will determine the future of the pandemic.”