City health officials and Rice University scientists have begun testing Houston wastewater samples for COVID-19, a process they hope will reveal the true spread of the new coronavirus as clinical testing continues to lag.
The city-led effort makes use of studies that show traces of the virus can be found in human feces. By testing samples of sewage collected at the city’s wastewater treatment plants, officials hope to uncover the scale of the outbreak in Houston and, perhaps, locate hotspots undetected by in-person tests.
“It’s an evolving field. We hope that it will help give us just more information on where the virus is and how much of it is out there,” said Loren Hopkins, a Rice University statistics professor who also serves as the health department’s chief environmental science officer.
For now, plant workers are collecting wastewater samples across a 24-hour period once a week, before sending them to Rice and health department officials who then analyze the samples for COVID-19, the illness caused by the new coronavirus.
If successful, the project will reveal COVID-19 trends over a span of weeks and months in certain areas of Houston and citywide, Hopkins said. Though less precise than directly testing people for the coronavirus, the analysis will produce case estimates that include people who lack symptoms, because asymptomatic people still shed the virus in their stool. And because workers at the treatment plants are collecting samples across a 24-hour period, the results may provide a more accurate snapshot than the number of positive in-person test results, Hopkins said, because that data is impaired by days-long delays in receiving results.
Where the data may prove especially useful, experts said, is in locations where wastewater samples indicate the virus has spread more widely than clinical testing has revealed. Officials can then direct more testing to those areas, including through a mobile unit that launched earlier this week.
This is an attempt to address the serious gap between our need for testing and our capacity for testing. We hope it will help identify trends and emerging hot spots more quickly and effectively. It’s something that’s not been done before, and who knows if it will work the way we want. It’s surely worth a try.