HTLV Prevalence by Geographic Location
The prevalence of HTLV infection varies dramatically by geographic location, ranging from 0.016% in the United States general blood donor population to as high as 15% in endemic regions such as southwestern Japan, the Caribbean basin, parts of Africa, and Melanesia 1.
Geographic Distribution
Endemic Regions (High Prevalence)
HTLV-I is endemic in specific geographic clusters with substantially elevated infection rates 1:
- Southwestern Japan: Up to 15% in general population
- Caribbean basin: Up to 15% in general population
- Melanesia: Up to 15% in general population
- Parts of Africa: Up to 15% in general population
Important caveat: Seroprevalence increases with age, and in older age groups, rates are consistently higher among women than men 1.
Low Prevalence Regions
United States: HTLV-I/II combined seroprevalence among volunteer blood donors averages 0.016%, with approximately half infected with HTLV-I and half with HTLV-II 1. Specific clusters exist among:
- Blacks from the southeastern United States
- Immigrants from HTLV-I-endemic areas (particularly Brooklyn, New York)
- Individuals with birth history in endemic countries or sexual contact with persons from Caribbean or Japan 1
Northern California blood donors: 0.055% confirmed HTLV antibody prevalence, with 63% HTLV-II and 30% HTLV-I 2.
Chile (Valdivia): 0.24% HTLV-1 seroprevalence among blood donors 3.
Peru: 2.5% among healthy women across diverse ethnic groups (1.3% in Andean Quechua population, 3.8% in African-American coastal communities, 3.8% in Lima Mestizo population) 4.
Global Patterns by Development Status
A critical finding from recent meta-analysis shows that HTLV-1 prevalence is approximately three times higher in low Human Development Index (HDI) countries [1.18%] compared to high HDI countries [0.41%] 5. The overall global prevalence is estimated at 0.91% 5.
Population-Specific Variations
Prevalence differs substantially by population studied 5:
- General population: 1.65% (highest risk)
- Pregnant women: 0.34% (5 times lower than general population)
- Blood donors: 0.04% (41 times lower than general population)
This pattern holds across both high and low HDI countries, though absolute rates are consistently higher in low HDI settings 5.
Immigrants and Refugees
Among immigrant and refugee populations worldwide, pooled HTLV-1 prevalence is 1.28%, with HTLV-2 at 0.11% 6. The highest prevalence occurs among those from the Western Pacific Region (7.27%) 6.
Clinical Implications
The geographic heterogeneity has direct implications for screening strategies. Blood donor screening identifies far lower rates (0.04%) than general population screening (1.65%), suggesting that targeted screening in endemic regions or high-risk populations is more epidemiologically relevant than universal blood donor screening alone 5.
Risk factors consistently associated with infection across geographic regions include: history of blood transfusion, age ≥38 years, multiple lifetime sexual partners (>4), low educational status, multiple pregnancies (>4), and in some regions, chronic scabies 4.