According to a study, school children in China, tracked with wearable devices, provide data on close contact behaviors that can influence viral transmission. Nan Zhang and her colleagues fitted wearable trackers to 24 children at a school made up of elementary, middle and high school students in Jiangsu Province, China.
Two volunteers were selected from each class, grades 1 through 12, and asked to sit near the middle of the class. For 45 minutes during class and 10 minutes during breaks between classes, the devices recorded the children’s interpersonal distance, face orientation, relative position (horizontal and vertical), close contact rate, and number of people through close contact. Close contact was defined as any face-to-face or face-to-side/back interaction between individuals within 1.5 meters. The authors collected 251,558 close contact event data points and found that younger children had higher close contact rates than older children. Most face-to-face contact took place during breaks. On average, children were in close contact with other children 37% of the time during lessons and 48% of the time during breaks. The authors estimate that most viral transmission of COVID-19 at school would be by long-distance airborne transmission, although short-distance airborne transmission is more likely during breaks, but only when no mask was on. door.
The rate of viral transmission was higher during breaks than during class, although transmission is generally of greater concern during class. The authors recommend a classroom ventilation rate of 30 cubic meters per hour per person, usually achievable with open windows in good weather and with fresh air systems at other times.
Guo, Y. et al. (2023) Close contact behavior of students and transmission of COVID-19 in classrooms in China. Nexus PNAS. doi.org/10.1093/pnasnexus/pgad142.