The proportion of children infected with COVID-19 while riding a bus to a school in Germany was about four times higher than in peers who didn’t ride the bus, illustrating efficient transmission during multiple short rides on public transport, finds a study published this week in Emerging Infectious Diseases.

A team led by researchers from the Robert Koch Institute in Berlin and public health officials used surveillance data, lab analyses, case-patient and household interviews, a cohort study of all students in grades 1 to 4, and a cohort study of bus riders to investigate a 2021 COVID-19 outbreak that involved an infected bus driver and his passengers. The rides lasted 9 to 18 minutes, and multiple schools in a single district were involved.