Why the tuberculosis incidence rate is not falling in New Zealand.
OBJECTIVE
To assess the role of migration from high-incidence countries, HIV/AIDS infection, and prevalence of multi-drug resistant organisms as contributors to tuberculosis (TB) incidence in New Zealand (NZ) relative to ongoing local transmission and reactivation of disease.


METHODS
TB notification data and laboratory data for the period 1995 to 2004 and population data from the 1996 and 2001 Census were used to calculate incidence rates of TB by age and ethnicity, country of birth (distinguishing high and low -incidence countries), and interval between migration and onset of disease. Published reports of multi-drug-resistant TB for the period 1995 to 2004 were reviewed. Anonymous HIV surveillance data held by AIDS Epidemiology Group were matched with coded and anonymised TB surveillance data to measure the extent of HIV/AIDS coinfection in notified TB cases.


RESULTS
Migration of people from high-TB incidence countries is the main source of TB in NZ. Of those who develop TB, a quarter does so within a year of migration, and a quarter of this group (mainly refugees) probably enter the country with pre-existing disease. Rates of local TB transmission and reactivation of old disease are declining steadily for NZ-born populations, except for NZ-born Maori and Pacific people under 40. HIV/AIDS and multi-drug-resistant organisms are not significant contributors to TB incidence in NZ and there is no indication that their role is increasing.


CONCLUSIONS
TB incidence is not decreasing in NZ mainly due to migration of TB infected people from high-incidence countries and subsequent development of active disease in some of them in NZ. This finding emphasises the importance of regional and global TB control initiatives. Refugees and migrants are not acting as an important source of TB for most NZ-born populations. Those caring for them should have a high level of clinical suspicion for TB.
Das
Dilip
D
Department of Public Health, Wellington School of Medicine and Health Sciences, University of Otago, Wellington.
Baker
Michael
M
Venugopal
Kamalesh
K
McAllister
Susan
S
D000163:Acquired Immunodeficiency Syndrome / Q000453:epidemiology / Q000208:ethnology; D000328:Adult; D000349:Africa / Q000208:ethnology; D017677:Age Distribution; D000368:Aged; D001208:Asia / Q000208:ethnology; D001315:Australia / Q000208:ethnology; D002648:Child; D015897:Comorbidity; D004196:Disease Outbreaks / Q000517:prevention & control*; D018432:Drug Resistance, Multiple / Q000208:ethnology; D004641:Emigration and Immigration / Q000706:statistics & numerical data*; D005060:Europe / Q000208:ethnology; D015658:HIV Infections / Q000453:epidemiology / Q000208:ethnology; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D009656:North America / Q000208:ethnology; D010139:Pacific Islands / Q000208:ethnology; D011159:Population Surveillance; D014376:Tuberculosis / Q000453:epidemiology* / Q000208:ethnology