An unvaccinated teacher at a primary school in California spread the coronavirus to at least 26 other people, including 12 students in their classroom.
This is according to a new study by the Centers for Disease Control and Prevention (CDC). The US health agency said the case highlights the importance of vaccinating school staff in order to protect young children who are not yet eligible for vaccines.
It comes as schools reopen across the US amid a new nationwide surge there driven by the ultra-contagious Delta variant. The CDC said the incident took place in Marin County, a suburb of San Francisco.
The teacher, who reported attending social functions from 13-16 May, became symptomatic on 19 May but did not take a Covid test until 21 May,