As Newton prepares to reopen high schools, COVID-19 surveillance testing will begin for staff Samuel Scarpino, a Northeastern University epidemiologist who did not sign the letter, said surveillance testing needs to be conducted at least once a week to be effective. “Everything I’ve seen suggests that anything longer than a week [and for sure less frequently than every-other-week] is unlikely to have an effect,” Scarpino said in an e-mail.