Occurence of food and water-borne diseases

  • Image, food and water borne diseases.

    Bacteria and parasites are influenced by climate variables, and infection rates may increase in response to climate change and rising temperatures. Campylobacter, Cryptosporidium, and Salmonella are three such organisms that can contaminate our food and water, leading to serious illness. Monitoring the incidence of illnesses can help us assess the health risks related to climate change and better prepare for potential increases in disease.

    We classified occurrence of food- and water-borne diseases as supporting information.

    Key findings

    Climate is not the only influence on infection rates (food- and water-borne diseases can occur at any time of year), but it is an important factor.

    • Notifications vary over the course of the year. From 2007 to 2016, the average monthly notifications for: 
      • campylobacteriosis were highest from November to January (850, 841, and 882, respectively) and lowest from April to July (428, 474, 418, and 461, respectively).

      • cryptosporidiosis were highest in September and October (164 and 168) and lowest in June, July, December, and January (40, 38, 34, and 43, respectively).

      • salmonellosis were highest from January to March (131, 120, and 117, respectively) and lowest from June to July (62 and 64, respectively).

    • The number of notified cases varied greatly from year to year. A range of voluntary and regulatory interventions since late 2006 coincided with a marked decline in Campylobacter cases (Sears et al, 2011).
    Figure 1
    Figure 2

    Definition and methodology

    A warming climate is expected to affect the infection rates of Campylobacter and Cryptosporidium (Tompkins et al, 2012), and Salmonella (WHO, nd). Cryptosporidiosis and salmonellosis are recommended environmental health indicators in New Zealand and are used to monitor the effectiveness of health interventions for climate change (Hambling, 2012).

    Campylobacter is a bacterium transmitted mainly by eating contaminated food or having contact with farm animals (as well as dogs and cats). Infection rates are strongly linked to temperature and tend to peak in summer. Campylobacteriosis is the most commonly notified disease, representing 43.5 percent of disease notifications in 2015 (Institute of Environmental Science and Research (ESR), 2016a). However, a range of voluntary and regulatory interventions since late 2006 coincided with a significant drop in Campylobacter cases (Sears et al, 2011).

    Cryptosporidium is a microscopic parasite transmitted mainly through water. Cryptosporidiosis rates can increase during extreme droughts, when reduced river flows and water levels increase the concentration of contaminants. Periods of heavy rainfall can also increase the number of cryptosporidiosis cases, when overflowing sewage systems may discharge untreated sewage into waterways. Effluent run-off can also increase the concentration of cryptosporidiosis microbes in water. Improved water treatment and other prevention measures are likely to reduce the incidence of cryptosporidiosis.

    Salmonella is a bacterium transmitted mainly by eating contaminated food. Warmer ambient temperatures allow the bacteria to grow faster in unrefrigerated foods, which may lead to higher infection rates.

    The numbers of notified cases of infection were sourced from EpiSurv, New Zealand’s national notifiable disease surveillance system. Various factors influence disease notification. For example, people are less likely to consult a medical practitioner when an illness is not severe (ESR, 2016a). The number of notified cases can vary greatly from year to year due to New Zealand’s small population and low number of cases for some diseases (ESR, 2016a). The August 2016 Camplylobacter outbreak in Havelock North provides an example of this variation (ESR, 2016b).

    Data quality

    We classified occurrence of food- and water-borne diseases as supporting information.


       This supporting information is an indirect measure of the ‘Impacts on public health' topic.


       The accuracy of the data source is of high quality.

    See Data quality information for more detail.


    Hambling, T (2012). Environmental health indicators: Development of a tool to assess and monitor the impacts of climate change on human health (PDF, 706kB). Retrieved from www.esr.cri.nz.

    Institute of Environmental Science and Research (ESR). (2016a). Notifiable diseases in New Zealand 2015 (PDF, 2MB). Retrieved from https://surv.esr.cri.nz.

    Institute of Environmental Science and Research (ESR). (2016b). Public health surveillance report December 2016: Covering July to September 2016 (PDF, 602kB). Retrieved from https://surv.esr.cri.nz.

    Sears, A, Baker, MG, Wilson, N, Marshall, J, Muellner, P, Campbell, DM,… French, NP (2011). Marked campylobacteriosis decline after interventions aimed at poultry, New Zealand. Emerging Infectious Diseases, 17(6), 1007–15. http://doi.org/10.3201/eid/1706.101272

    Tompkins, D, Brock, A, Jones, G, Mcbride, G, Tait, A, Benschop, J, … Slaney, D (2012). Modelling the impacts of climate change on infectious diseases in New Zealand (PDF, 6MB). Retrieved from www.esr.cri.nz.

    World Health Organization (nd). Data and statistics. Retrieved 17 July 2017 from http://www.euro.who.int.

    Archived webpages

    See Food- and water-borne diseases (archived October 2017).

    Updated 19 October 2017

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