The spatial distribution of campylobacteriosis in New Zealand, 1997-2005

In New Zealand Campylobacter infection rates have increased steadily since 1980, reaching a peak in 2003 (396/100 000 population). Compared to other nations, disease rates are unfavourably high (e.g. Australia 117/100 000 population, UK 85/100 000 population, USA 13/100 000 population). This ecological study investigated spatial variations in Campylobacter infection rates across New Zealand's Territorial Local Authorities (TLAs, n = 73) for the period 1997-2005. Applying multiple linear regression, we examined whether geographical factors such as socio-demographic characteristics, climate, land use, water and the food environment were associated with local differences in the occurrence of Campylobacter infection rates. The results suggested significant variations in campylobacteriosis across TLAs (average annual rates ranging from 97 to 526/100 000 population), with higher rates in the South Island. Disease rates were associated with lower socio-economic deprivation (P < 0.01), the proportion of the population aged 25-44 years (P < 0.01) and fresh food outlet density (P < 0.76). The results underline the role of area-level characteristics in explaining the spatial distribution of campylobacteriosis in New Zealand. In particular, the findings draw attention to the relatively unexplored role of fresh food outlets as a potential risk factor for increased Campylobacter notifications.