The United States this week also expanded its voluntary genomic sequencing program at airports, adding Seattle and Los Angeles to the program. "Previous COVID-19 wastewater surveillance has shown to be a valuable tool and airplane wastewater surveillance could potentially be an option," she wrote. French researchers reported in July that airplane wastewater tests showed requiring negative COVID tests before international flights does not protect countries from the spread of new variants. They found the Omicron variant in wastewater from two commercial airplanes that flew from Ethiopia to France in December 2021 even though passengers had been required to take COVID tests before boarding. Osterholm and others said mandatory testing before travel to the United States is unlikely to keep new variants out of the country.

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