PhD thesis - University of Hertfordshire Research Archive

Conclusions.
Case-control studies of Campylobacter infection are increasing in size
and complexity without the corresponding improvement in our
understanding of disease transmission.
The move towards larger studies are perhaps magnifying the biases
inherent in the methodology.
They appear to be influenced heavily by investigator and reporter bias,
as evidenced by the disproportionate pursuit of the poultry hypothesis,
which continues to explain only a fraction of cases, emphasising the
need for more creative approaches to hypothesis generation.
166