HARRISBURG (AP) — Pennsylvania’s coronavirus exposure notification app can now be used by mobile phone users as young as 13 as health officials work to stop the virus’ spread in schools. The app, named COVID AlertPa, had been limited to people 18 and over. State Health Secretary Dr. Rachel Levine says middle- and high-school students can add their phones to help contact tracing in schools if a positive case is identified. A parent or legal guardian must approve the minor’s use of the app. Some school districts continue to conduct in-person instruction, even though every county except one has passed new case thresholds where the state Department of Education recommended fully remote instruction.