Environmental Health Indicators

Monitoring the health effects of climate change

This section describes statistics on four climate-sensitive infectious diseases in Aotearoa New Zealand: campylobacteriosis, giardiasis, cryptosporidiosis and salmonellosis.

Factsheets and Metadata

Factsheet: Gastrointestinal diseases linked to climate change (September 2022) View interactive report Download report PDF

Metadata: Gastrointestinal diseases linked to climate change Download report PDF

A warmer climate has several effects on health

Climate change has been described as “the biggest global health threat in the 21^st century” [1].

Studies show that cryptosporidiosis and giardiasis (gastro-intestinal ‘tummy bug’ infections) are affected by rainfall patterns. Cryptosporidiosis and giardiasis can be caught by drinking water that has been contaminated with cryptosporidium and/or giardia cysts. High rainfall events can wash cysts from fields into water sources [3]. Drought conditions can lead to a greater concentration of cysts in rivers due to low water flow and volume [2].

Higher temperatures are linked to an increase in salmonellosis notifications. Salmonellosis (gastro-intestinal ‘tummy bug’ infection) can be contracted by eating or drinking food and/or water that has been contaminated by humans or animals with the Salmonella bacteria. An increase of 1°C in monthly average temperatures has been associated with 15% more salmonellosis notifications in that month [4].

Aside from gastrointestinal diseases, a warming climate may exacerbate other health problems, including:

infectious diseases: Increasing temperatures can change the geographical distribution of some mosquitoes, carrying infectious diseases.
respiratory problems: Increasing temperatures bring a longer pollen season and increased fire risk, associated with increases in respiratory problems.
cardiac (heart) problems: Heat is linked to worsening of heart problems and to an increase in overall death rates (Hales et al 2007; McMichael et al 2003).

Climate-sensitive disease indicators

Studies have also shown a positive association with higher temperatures and heavy rainfalls increasing the risk of campylobacteriosis outbreaks, such as in Havelock North in 2016.

Droughts and changing rainfall patterns have several effects on health

drinking water: Severe drought can reduce the quality and the amount of drinking water available. New Zealand’s populations that rely on rainwater tanks for their drinking water supply can be particularly affected.
gastrointestinal infections: Rates of the gastrointestinal infections, campylobacteriosis, cryptosporidiosis and giardiasis are affected by rainfall patterns. Rainfall washes giardia and cryptosporidium cysts, or campylobacter bacteria into waterways, where they can contaminate drinking water sources. Drought conditions can lead to a greater cyst concentration in groundwater and surface water sources (Britton et al 2010; Lal et al 2013).
crop production: Drought can reduce crop production, meaning there is less (and possibly more expensive) food available for consumption. Food from fresh water sources will also be diminished.
effect on mental health: Drought can have a significant effect on mental health, particularly for those in rural areas who rely on rain for their livelihoods.

Ongoing monitoring of the health effects of climate change is needed

Climate change trends occur over many years, so correspondingly long-term health data are needed to show changes in disease occurrence and severity due to climate change.

However, it is useful to monitor the likely health effects of climate change in place, in anticipation of possible increases and changes in patterns of diseases. Monitoring data on aspects of the environment and vulnerable populations is also needed to sit alongside monitoring of health effects, as is data at the regional level.

Information about the data

Specific change over time corresponding with climate change cannot be shown as the common baseline period in climate change science is 1960-1990, for which comparable data is not available.

Notifications of gastrointestinal diseases

Source: EpiSurv, ESR

Definition: This indicator presents campylobacteriosis, salmonellosis, giardiasis and cryptosporidiosis notifications. Notifications where the person was overseas during the incubation period have been excluded. Notifications only cover those people who visited a GP or hospital for treatment, and may therefore underestimate the disease rate. Rates presented are per 100,000 people (or 100,000 people per year for combined data over 10-year periods). Age-standardised rates have been presented where possible, to take into account the population age structures of different population groups.

References

Costello A, Abbas M, Allen A, et al. 2009. Managing the health effects of climate change. The Lancet 373(9676): 1693-1733. DOI: 10.1016/S0140-6736(09)60935-1 (accessed 4 December 2018).
Lal A, Baker MG, Hales S, et al. 2013. Potential effects of global environmental changes on cryptosporidiosis and giardiasis transmission. Trends in Parasitology 29(2): 83-90. DOI: 10.1016/j.pt.2012.10.005 (accessed 5 December 2018).
Britton E, Hales S, Venugopal K, et al. 2010. The impact of climate variability and change on cryptosporidiosis and giardiasis rates in New Zealand. Journal of Water and Health 8(3): 561-71. DOI: 10.2166/wh.2010.049 (accessed 5 December 2018).
Britton E, Hales S, Venugopal K, et al. 2010. Positive association between ambient temperature and salmonellosis notifications in New Zealand, 1965-2006. Australian and New Zealand Journal of Public Health 34(2): 126-9. DOI: 10.1111/j.1753-6405.2010.00495.x (accessed 5 December 2018).
Gilpin B, Walker T, Paine S, et al. 2020. A large scale waterborne Campylobacteriosis outbreak, Havelock North, New Zealand. Journal of Infection 81(3):390-95. https://doi.org/10.1016/j.jinf.2020.06.065 Zealand Journal of Public Health (accessed 7 July 2022).