One of the more innovative, if not grosser, ways of determining where a coronavirus outbreak will hit is being used by officials in Tempe, Arizona, who have been testing wastewater to determine who needs to be quarantined.
The Washington Examiner reported last week that testing wastewater led to officials in Tempe quarantining a portion of the city they called “Area 6,” who were infected with the virus and may not have known.
“Wastewater is a lead indicator [of a virus outbreak], while people testing positive is a lag indicator,” Rosa Inchausti, director of strategic management and diversity for the city of Tempe, told the Examiner. “Wastewater is a lead indicator because people shed the virus up to seven days prior to showing symptoms.”
Area 6, Inchausti told the outlet, contains some of the poorest residents of Tempe, many of them immigrants with multiple generations living in the same residence. In those situations, quarantining was difficult, but the city was able to place families infected with the coronavirus in a local motel so that they could quarantine.
“No one’s traveling and using hotels,” Inchausti told the Examiner. “It was a great way to use resources and partner with the business community.”
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Individuals excrete the virus through feces, so testing sewage can inform officials when more people are being infected before they are likely to show up at the hospital. The more targeted the testing, the more focused public health efforts can be. Tempe is able to identify concentrations of the virus by testing the wastewater in seven different areas three times a week.
Area 6 of Tempe is a small area in the center of the city adjacent to Arizona State University. In early September, it started showing high amounts of the coronavirus in the wastewater. Authorities began offering saliva-based testing for the virus through the schools in Area 6 and hand-delivering masks to homes and businesses. The city also partnered with nonprofit groups to do outreach and to educate residents about proper safety protocols. This enabled officials to identify infected people who were living in crowded conditions and to isolate them.
Continued testing of wastewater in Tempe has shown a reduction in the coronavirus, though Inchausti cautioned against attributing it all to their quarantine measures.
“We did see the numbers come down, although we can’t say that has all been because of this deployment of services,” she told the Examiner.
The outlet reported that Tempe does its own testing, while many other cities send samples to companies that do the testing for them. Many cities can’t afford the testing, however.
“It’s not cheap, so the more sample sites you go to and analyze, the more it costs,” Christoph Dobson, director of policy and planning at the Sacramento Area Sewer District, told the Examiner. “We have thought about [sampling more sites], but it has to be in the context of what is the benefit of that information and how much does it cost?”
Arizona has had more than 265,000 cases of coronavirus this year, and 6,228 people have died from the disease in the state.