Epidemiology of Leprosy (Hansen Disease) in Washington State, 2001-2023

Abstract

Objectives: Since 2000, leprosy has not been notifiable in Washington State, and statewide leprosy data have not been reported. We sought to increase our understanding of leprosy epidemiology in Washington State since 2001.

Methods: We reviewed data from the National Hansen's Disease Program to identify clinically diagnosed leprosy cases from 2001 through 2023 among Washington State residents. We analyzed cases over time, by county of residence, disease type, and global birth region. We used Poisson regression to estimate rates by birth region and incidence rate ratios to compare rates among US-born residents and those from other global birth regions.

Results: We identified 131 cases of leprosy in Washington State from 2001 through 2023. Most cases were among non-US-born people (95%), males (72%), and adults aged 18 to 64 years (87%); one-third were among Micronesian or Marshallese people. As compared with US-born people (0.2 per 1 000 000 population), the leprosy rate was 1064 times (95% CI, 466-3069) higher among people born in Oceania (215 per 1 000 000 population). Incidence rate ratios for other birth regions ranged from 301 (95% CI, 43-1396) for South America to 28 (95% CI, 11-82) for Asia.

Conclusions: Focused public health interventions, including increased physician awareness of leprosy and its stigma for populations at high risk, may reduce the incidence of leprosy among Washington State residents born in Oceania, who had a disproportionately high disease rate.

Keywords: Hansen disease; Hansen’s disease; leprosy.

Figure 1.

Cases of Hansen disease reported to the National Hansen’s Disease Program in Washington State, by region of birth, 2001-2023. Data source: National Hansen’s Disease Program.

Figure 2.

Distribution of disease type, by region of birth, for cases of Hansen disease reported to the National Hansen’s Disease Program in Washington State, 2001-2023. Excludes 4 cases with unknown region of birth. World Health Organization disease types: paucibacillary is ≤5 skin lesions and is generally equivalent to indeterminate, tuberculoid, or borderline tuberculoid disease on the Ridley–Jopling classification; multibacillary is ≥6 skin lesions and generally equivalent to borderline, borderline lepromatous, or lepromatous disease on the Ridley–Jopling classification. Data source: National Hansen’s Disease Program.

Figure 3.

Annual rate of Hansen disease per 1 000 000 population reported to the National Hansen’s Disease Program in Washington State, by region of birth, 2010-2023. Denominators are from the US Census Bureau American Community Survey and are available from 2010 onward. Excludes 4 cases with unknown region of birth. Data source: National Hansen’s Disease Program.