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Immigrants and the Spread of Tuberculosis in the United States: A Hidden Cost of Immigration

Immigrants and the Spread of Tuberculosis in the United States: A Hidden Cost of Immigration. by, Michael J. Greenwood and Watson R. Warriner. Research Question and Motivation.

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Immigrants and the Spread of Tuberculosis in the United States: A Hidden Cost of Immigration

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  1. Immigrants and the Spread of Tuberculosis in the United States:A Hidden Cost of Immigration by, Michael J. Greenwood and Watson R. Warriner

  2. Research Question and Motivation Do immigrants from countries with high TB incidence affect Tuberculosis cases among the foreign-born population, and in turn, is the native-born population in the United States infected? • TB is the second largest killer from infectious diseases in the world • TB Prevalence is on the rise around the world • TB rates in the U.S. continue to decline, but by less each year • Does something have to give? • Is there transmission between cohorts?

  3. Figure 1. TB Incidence Map (2006)

  4. Figure 2. HIV Prevalence Map (2007)

  5. Notes: Data obtained from the CDC Wonder OTIS Database and U.S. Census Bureau

  6. Notes: Data obtained from World Health Organization Tuberculosis Programme

  7. Notes: Data obtained from the CDC Wonder OTIS Database and U.S. Census Bureau

  8. TB Background • Types • Latent or Active • Treatments • Chemotherapy (four different drugs for 6 months) • BCG (Bacillus Calmette-Guerin) Vaccine – not effective for active or re-activations • Immigration Laws • Persons with TB not allowed into the U.S. • Prior to 2007: chest x-ray (only detects active) • 2007 to Present: skin test for children under 15 (detects both active and latent forms)

  9. Related Research • Little research regarding immigrant to native transmission • Stagnation in TB elimination relatively recent • Immigration has not been a primary focus in TB elimination efforts • Small-scale case studies vs. larger-scale epidemiological studies • Conclusions • Positively correlated with TB: • Number of minorities, population density, immigration, poverty, and HIV/AIDS • Findings are inconsistent • No research on transmission to native-born populations

  10. Theoretical Background • Top 50 Metropolitan Statistical Areas (MSAs) by total TB cases (1993-2007) • Limitation due to suppression of TB statistics • Account for 69.5% of total TB cases in the U.S. (1993-2007) • Observation = an MSA in a given year • 750 total (15 years x 50 MSAs)

  11. Theoretical Background • Recursive Model (A -> B, B -> C) • A: High-Incidence Immigration • B: Foreign-Born TB • C: Native-Born TB 1. FBTBit = f(HMIGit , LMIGit, DEMit , SOCECONit) 2. NBTBit = g (FBTBit , DEMit ,SOCECONit)

  12. Data • Tuberculosis Statistics • Constant geographies: 2007 MSA definitions • Demographic and socio-economic data • Country-specific TB incidence data • MSA immigration statistics • HIV incidence data

  13. * Not in Regressions

  14. Econometric Approach • Double-log regression • Results can be interpreted as elasticities • Or…the percentage change in the dependant variable that results from a one-percent change in the independent variable • FBTBit = α1(HMIGit β1) (LMIGit β2 ) (FBPopit β3) (NBPopit β4) (PopDenit β5) (Povertyit β6)( εit ) 2. NBTBit = α2(FBTBit ρ1) (NBPopit ρ2) (FBPopit ρ3 ) (Whiteit ρ4 ) (Blackit ρ5 ) (Asianit ρ6 ) (AmerIndit ρ7 ) (OtherRaceit ρ8 ) (Hispanicit ρ9 ) (PopDenit ρ10 ) (Povertyit ρ11 ) ( εit )

  15. Econometric Approach • Five Estimations per Regression • FOCUS: Temporal and Divisional (9 Census Divisions) Fixed Effects • Base Year = 1993, Base Division = Pacific • Immigration Variable is Summed, t and t-1 • HIV/AIDS Incidence Inclusion • 2006, 12% TB cases in U.S. were also co-infections with HIV • Data Limited to 2003 – 2007 (Panel Data with 250 Observations) • Only an estimated effect

  16. Empirical Results • Positive and significant elasticities for key independent variables in both regressions • Increased immigration from high-TB incidence countries -> increased number of TB cases among the foreign-born -> more native-born TB cases • Transmission exists from the foreign to the native-born populations in the sample

  17. Societal Cost of TB in U.S. for 2008 • Societal Cost Makeup • $1.47 billion - $2.63 billion (not including transmission) • 0.018% of total GDP ($14.61 trillion) • TST for all LPR Immigrants = $23.8 million • Between 0.90% and 1.62% of total TB cost • Minor relative cost to eliminate incoming TB

  18. Discussion • Advantages • Broad sample and isolation of urban areas • Limitations • Linear interpolation of demographic data • Demographic data only gathered for entire population • Immigration data only include Legal Permanent Residents • Extensions • Two way transmission – two staged least squares • Obtain more years for HIV incidence data

  19. Implications of Research • Incoming latent TB among Immigrants infecting the natives through transmission via the foreign-born population • TST for all immigrants highly recommended • HIV Travel Ban Lifted in 2009 • Major Implications to this study • 1/3 of those infected with HIV are TB co-infections

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