Last Updated: 2009-12-10 20:27:47 -0400 (Reuters Health)

NEW YORK (Reuters Health) – The 2009 pandemic influenza A (H1N1) virus hit American Indians and Alaska natives much harder than all other racial/ethnic populations combined, with overall mortality rates that were 4-fold higher than rates in all other racial and ethnic groups combined.

Dr. L. Castrodale, from the Alaska Division of Public Health, and associates theorize that the higher mortality rate among American Indians and Alaska natives — reported in the Morbidity and Mortality Weekly Report for December 11 — could be due to their higher prevalence of chronic health conditions, poor living conditions, and delayed access to care.

In November 2009, 12 state health departments volunteered to provide data on influenza-related deaths among their residents.

Because more than 99% of influenza specimens tested during the study period had been H1N1, the study investigators presumed that all patients with a positive influenza test were infected with H1N1 and not seasonal influenza.

The states reported that between April 15 and November 13, of all 426 H1N1 deaths that occurred, 42 (9.9%) occurred among American Indians and Alaska natives, even though this group makes up only about 3% of the total population in the 12 states.

The overall American Indian and Alaska native H1N1-related death rate was 3.7 per 100,000 population, compared with 0.9 per 100,000 for all other groups combined, yielding a mortality rate ratio of 4.0.

Dr. Castrodale’s team points out that higher proportions of American Indian and Alaska native decedents had asthma and diabetes than the decedents of other racial/ethnic populations combined (31.0% vs 14.1% for asthma, 45.2% vs 24.0% for diabetes).

Age-specific mortality rate ratios were 2.7 among individuals between 5-24 years old, 3.7 among 26- to 64-year-olds, 5.0 among older individuals, and 7.2 among newborns to 4 years of age.

Authors of an editorial point out that this pattern has been observed in other parts of the world during the current H1N1 pandemic and also in previous pandemics. For example, during the 1918-1919 influenza pandemic as well, influenza-related mortality rates among American Indians and Alaska natives were 4-fold higher than among persons in the general urban population.

They conclude: "Health professionals and agencies should expand community education regarding the risk for influenza mortality, ensure access to and early empiric use of influenza antiviral medication, promote H1N1 vaccination, and investigate factors contributing to a higher influenza-related mortality rate among American Indians and Alaska natives.

Mor Mortal Wkly Rep CDC Surveill Summ 2009;58:1341-1344.