Data on attitudes, knowledge, situational awareness, risk perception and preventive behaviours (Table S1) were collected by household telephone interviews, based on random digit dialling. One Cantonese-speaking adult (age$18) who lives .4 nights per week in each household was selected using a Kish grid. All interviews were conducted between 8:30pm-10:45pm from 23 rd -25 th June, 2009, two weeks after the first community transmission had been identified in Hong Kong. 