Figure 2. Hansen disease in patients of Marshallese or Micronesian origin, US mainland, by year reported, January 1990–October 2009. being identiﬁed than during the usual passive surveillance years (Table 2); this pattern was also noted in the 1998 Marshallese cluster in Hawaii. Hansen Disease, United States Discussion This study was descriptive; thus, comparisons among the various population subgroups are not statistically valid because of small numbers, varied data sources, and unknown age/sex distribution and denominators for the overall migrant populations. However, because age and sex distributions for the Arkansas, Hawaii, and Republic of the Marshall Islands Marshallese populations are similar (17), some crude comparisons can be made for these groups. Unless an unidentiﬁed confounder is present, rates and distribution of cases would be expected to be similar in the 3 groups. The Arkansas and Hawaii Marshallese populations were approximately the same size (3,000 each) and age/sex distribution (median age 20 years, M:F = 1) in 1998–2001; rough estimates place the current Arkansas population at 8,000–10,000 and Hawaii at 6,000–8,000. However, Hawaii has identiﬁed 2.6× more cases since 2000, more female patients, and more paucibacillary disease and has found disease in children. Estimated case detection rates for Arkansas Marshallese persons are approximately half those for the Marshall Islands (Figure 6) and more skewed toward multibacillary disease, male, and adult patients (Table 1). This Arkansas and general US mainland pattern of predominantly multibacillary disease in men does not reﬂect disease distribution patterns in the countries of origin or in Hawaii, suggesting under-detection of child, female, and paucibacillary disease patients rather than a biologic disease pattern (Tables 1, 2). Of 49 mainland patients from both the Federated States of Micronesia and the Marshall Islands for whom Figure 3. States reporting Hansen disease in patients of Marshallese or Micronesian origin, US mainland, January 1990–October 2009. The number of cases reported from each state is indicated. Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 7, July 2011 1205