摘要：Objectives. We estimated age-standardized ratios of infection and hospitalization among Canadian First Nations (FN) populations and compared their distributions with those estimated for non-FN populations in Manitoba, Canada. Methods. For the spring and fall 2009 waves of the H1N1 pandemic, we obtained daily numbers of laboratory-confirmed and hospitalized cases of H1N1 infection, stratified by 5-year age groups and FN status. We calculated age-standardized ratios with confidence intervals for each wave and compared ratios between age groups in each ethnic group and between the 2 waves for FN and non-FN populations. Results. Incidence and hospitalization ratios in all FN age groups during the first wave were significantly higher than those in non-FN age groups ( P < .001). The highest ratios were observed in FN young children aged 0 to 4 years. During the second wave, these ratios tended to decrease in FN populations and increase in non-FN populations, especially among groups younger than 30 years. Conclusions. Incidence and hospitalization ratios in FN populations were higher than or equivalent to ratios in non-FN populations. Our findings support the need to develop targeted prevention and control strategies specifically for vulnerable FN and remote communities. One striking aspect of the 2009 H1N1 influenza pandemic in Canada was its disproportionate impact on indigenous populations. In particular, on-reserve First Nations (FN) populations experienced severe disease outcomes often necessitating hospitalization and intensive care unit (ICU) admission. 1–4 Many of the affected FN communities are located in the northern Manitoba region, which has predominantly Aboriginal populations (76%), and are considered remote or isolated. 5 During the first pandemic wave, Winnipeg, an urban center in the province of Manitoba, experienced full occupancy of ICU beds at the peak of the outbreak in June 2009. 1 Among laboratory-confirmed cases reported during the first wave in Manitoba, 32% were individuals with registry status as FN, an ethnic group that constitutes approximately 7% of the province’s total population ( Table 1 ). According to the 2006 census data, 45% of this ethnic group in Manitoba resides off reserve. For community cases reported during the 2009 pandemic, FN status was determined by merging demographic data with a copy of the Indian Registry obtained from Indian and Northern Affairs Canada. The FN ethnic group refers to the Canadian Aboriginal peoples (with or without registry status) who are neither Inuit nor Métis. 6 As observed in other geographic regions, 7 the 2009 pandemic in Manitoba predominantly affected young adults and children in both spring and fall waves; however, the effect of the epidemic on FN populations has not been described. TABLE 1— Population Fraction, Laboratory-Confirmed Cases, and Number of Hospitalizations Among FN and Non-FN Populations: Manitoba, Canada; Spring and Fall 2009 Aged 0–4 Y Aged 5–19 Y Aged 20–49 Y Aged ≥ 50 Y Variable FN Non-FN FN Non-FN FN Non-FN FN Non-FN Population fraction .01 .053 .024 .18 .029 .38 .0086 .32 Laboratory-confirmed cases, no. First wave 86 52 93 179 82 276 19 96 Second wave 33 154 81 639 90 620 10 155 Hospitalizations, no. First wave 46 16 19 18 39 38 10 27 Second wave 3 18 5 28 14 55 5 38 Open in a separate window Note. FN = First Nations. We sought to estimate the age distribution of infection and hospitalization among the FN populations and compare those distributions with those estimated for non-FN populations. Our primary objective was to estimate the relative infection and hospitalization ratios by age group using laboratory-confirmed cases of H1N1 infection and to explore possible differences in age-specific patterns of infection and hospitalization. Our secondary objective was to identify possible shifts in patterns in age distribution between the first and second waves of the H1N1 pandemic in Manitoba.
