During the study period, from 1 June until 15 October 2010, 315 patients with confirmed influenza A were admitted to an ICU, compared with 1,113 patients during the same corresponding period in 2009. The predominant sub-type was H1N1 2009 in both years (90% in 2010 versus 83% in 2009, P = 0.002). The distribution of sub-types of influenza A is reported in Table 1 . In 2010 there were 283 patients with confirmed H1N1 2009 admitted to ICU, corresponding to a population incidence of admission to ICU of 10.6 (95% CI, 9.4 to 11.9) per million inhabitants [7, 8] . By comparison, during 2009 there were almost three times as many patients with confirmed H1N1 2009 (n = 921), corresponding to a population incidence of admission to ICU of 35.2 (95% CI, 32.9 to 37.5) per million inhabitants [7, 8] (P < 0.001). The geographical distribution of admissions was also different between 2010 and 2009 (Table 1 ). In 2010 the population incidence in Australia was 2-fold lower than in New Zealand (P < 0.001), whereas in 2009 this relationship was reversed with a 1.3-fold higher incidence in Australia (P = 0.009). The overall incidence, combining 2009 and 2010, was 45.3 (95% CI, 42.4 to 48.2) admission to ICU per million inhabitants in Australia and 47.1 (95% CI, 40.5 to 53.7) in New Zealand (P = 0.65).