Using the notified Tuberculosis data from ESR and data from the 1996 and 2001 censuses we used ecological modelling at the CAU level to examine the effect of household crowding on tuberculosis. We included the proportion of migrants in an area and area characteristics (such as deprivation as measured by NZDep).We found that although some migrants arrive in New Zealand with tuberculosis they do not spread it to the wider New Zealand population.

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Here are papers from the New Zealand Medical Journal explaining our results in more detail.
Tuberculosis epidemiology in New Zealand: 1995–2004 NZMJ 2006
Why the tuberculosis incidence rate is not falling in New Zealand NZMJ 2006