Researchers have claimed that children infected with swine flu are three times more likely to transmit the virus to those of their own gender than members of the opposite sex.
The study, carried out at an elementary school in Pennsylvania, US, also reported that rates of passing on flu were five times higher between classmates than between pupils from a different class. However, merely sitting next to a child with flu did not significantly increase chances of catching it.
A total of 370 pupils from 295 families took part in the study, with scientists looking at attendance records, bus schedules, nurse logs, seating charts and timetables to gauge levels of flu transmission across different settings.
Study leader Dr Simon Cauchemez, from the Medical Research Council's Centre for Outbreak Analysis and Modelling at Imperial College London, said: "This is one of the most comprehensive studies to date on how a flu epidemic spreads between children in school, and it tells us a great deal about how social networks influence transmission.
"The data from this study will help us make more accurate models, which can help public health officials to handle epidemics effectively."