Swine flu A/H1N1: Deaths related, American Indian/Alaska Natives

Indigenous populations from Australia, Canada, and New Zealand have been found to have a three to eight times higher rate of hospitalization and death associated with infection with the 2009 pandemic influenza A (H1N1) virus (1). In October, two U.S. states (Arizona and New Mexico) observed a disproportionate number of deaths related to H1N1 among American Indian/Alaska Natives (AI/ANs). These observations, plus incomplete reporting of race/ethnicity at the national level, led to formation of a multidisciplinary workgroup comprised of representatives from 12 state health departments, the Council of State and Territorial Epidemiologists, tribal epidemiology centers, the Indian Health Service, and CDC. The workgroup assessed the burden of H1N1 influenza deaths in the AI/AN population by compiling surveillance data from the states and comparing death rates. The results indicated that, during April 15--November 13, AI/ANs in the 12 participating states had an H1N1 mortality rate four times higher than persons in all other racial/ethnic populations combined. Reasons for this disparity in death rates are unknown and need further investigation; however, they might include a high prevalence of chronic health conditions (e.g., diabetes and asthma) among AI/ANs that predisposes them to influenza complications, poverty (e.g., poor living conditions), and delayed access to care. Efforts are needed to increase awareness among AI/ANs and their health-care providers of the potential severity of influenza and current recommendations regarding the timely use of antiviral medications. Efforts to promote the use of 2009 H1N1 influenza monovalent vaccine in AI/AN populations should be expanded.

In November 2009, all state health departments were invited to participate in the workgroup investigation by providing data on influenza-related deaths among their residents. Twelve states (Alabama, Alaska, Arizona, Michigan, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Utah, Washington, and Wyoming) chose to participate, representing 50% of the AI/AN population in the United States. An H1N1 death was defined as a death in a resident of a participating state reported during April 15--November 13 with any positive result from an influenza test, including rapid enzyme immunoassay, direct or indirect influenza fluorescent antibody, real-time reverse transcription--polymerase chain reaction assay (rRT-PCR), or viral culture. Because >99% of influenza specimens tested during the study period had been found to be H1N1, all cases with a positive influenza test were presumed to be H1N1 and not seasonal influenza. Race/ethnicity and influenza risk status of decedents were determined through review of death certificates, medical records, or death investigation reports. CDC-defined groups at higher risk for influenza complications were used to classify decedents as at high risk for influenza complications. Bridged-race vintage 2008 postcensal population estimates were used by all states to determine population data for rate calculations. Death rates by race/ethnicity were age adjusted to the 2000 U.S. standard population. Using rate ratios, AI/AN death rates were compared with death rates for all other racial/ethnic populations, including deaths in persons of unknown race.

A total of 426 H1N1 deaths were reported by the 12 states during April 15--November 13. Forty-two deaths (9.9%) occurred among AI/ANs, although AI/ANs make up approximately 3% of the total population in the 12 states. The overall AI/AN H1N1-related death rate was 3.7 per 100,000 population, compared with 0.9 per 100,000 for all other racial/ethnic populations combined,** resulting in a mortality rate ratio of 4.0. Age group--specific H1N1-related death rates were 3.5 for persons aged 0--4 years, 1.1 for persons aged 5--24 years, 4.2 for persons aged 25--64 years, and 7.2 for persons aged ≥65 years. In all age groups, the AI/AN death rate was higher than the rate for all other racial/ethnic populations combined.

Among the AI/AN deaths related to H1N1, 81.0% of decedents had high-risk health conditions, compared with 77.6% of persons in all other racial/ethnic populations combined. In addition, greater percentages of AI/AN decedents had asthma (31.0%) and diabetes (45.2%) than decedents in all other racial/ethnic populations combined (14.1% asthma and 24.0% diabetes).