To assess the distribution of illness by industry sector and occupation reflected in early 2009 H1N1 influenza surveillance. We analyzed data reported for April to July 2009, for 1361 laboratory-confirmed 2009 H1N1 influenza-infected persons 16 years or older, with work status information from four states. A North American Industry Classification System 2007 code was assigned to each employed person. For a subset, an occupation code was assigned. Of 898 employed individuals, 611 (68.0%) worked in the non-health care sector. The largest proportions worked in public administration, educational services, and accommodation and food services. In Wisconsin health care personnel, 53.6% were paraprofessionals, 33.6% professionals, and 12.7% other workers; 26.9% worked in ambulatory settings, 46.2% in hospitals, and 26.9% in nursing or residential care facilities. Our findings suggest that industry sectors and occupations should be explored systematically in future influenza surveillance.