PhD thesis - University of Hertfordshire Research Archive

community was no different from other recognised ethnic groups, although
the number of cases in this group was small. Pakistani cases tended to be
male and under five year olds were over-represented . Pakistani cases older
than one year were more likely to experience a longer illness and more often
required hospital treatment than their White counterparts. The seasonality of
infection also differed amongst resident Pakistanis, with more illness at the
beginning and end of the calendar year. A number of exposure differences
between resident Pakistani and White cases were apparent.
This study identified a distinct pattern of infection for Pakistanis resident in
England and Wales which could not be explained by recent foreign travel to
high-incidence destinations as described previously (paper 3
(Campylobacter Sentinel Surveillance Scheme Collaborators, 2003b)).
Indeed, a developing country pattern of disease was observed amongst
Pakistanis resident in a developed country, with high incidence in infants and
young children and little disease in adulthood. This suggests community-
specific routes of transmission and accompanying disease burden,
necessitating studies to identify risk factors for infection specific to this
community, or to assess alternative explanations for these observations (e.g.
use of healthcare facilities, prior immunity in older children, adults etc).
Several methodological issues were identified in this study which warrant
comment. Firstly, data from the 2001 census was unavailable at the time of
the study, so ethnicity-specific denominator data from the 1991 census was
used, and therefore the numerator and denominator differed by eleven years.
It is possible, therefore, that the observed differences in risk might relate to
changes in underlying population structure in the intervening period. This was
considered unlikely as such changes would not explain the clinical,
demographic, seasonal and exposure characteristics distinct to Pakistani
cases. Secondly, we elected to ask patients to describe their ethnic origin
rather than providing a choice of categories, meaning that for over a tenth of
patients a description was not provided or was not classifiable. This could
have skewed our findings if certain ethnic groups were more or less likely to
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