Dengue patients in the Mahidol Tropical Medicine Hospital

How can modelling be applied to human health?

The challenge is to understand how the key factors affecting health will be altered by climate change

One approach is to sift through historical data to look for correlations between a past change in climate and human health. So a change in rainfall might have been linked to an increase in the spread of cholera, or a rise in sun exposure to additional skin cancers.

A related approach is to look for climate variables that show correlations with the incidence of disease – typically infectious disease. A good example is the spread of dengue fever, caused by the world’s most common mosquito-borne virus.

Maps of Zimbabwe showing climate suitability for malaria transmission now and in 2050

Danger zones: Modelled climate suitability for malaria transmission across Zimbabwe in 2000 (left) and 2050 (right); red and orange areas are most suitable for transmission.

Credit:Left map (2000): Ebi KL et al. Climate suitability for stable malaria transmission in Zimbabwe under different climate change scenarios. Climatic Change 2005;73:375–93. Right map (2050): adapted by JA Patz and SH Olson.

Numbers of dengue-carrying mosquitoes are strongly dependent on temperature, moisture levels and sunshine. Indeed, a computer simulation used to predict mosquito numbers on the basis of these variables provided a good match for the yearly incidence of dengue disease in a range of countries, from Honduras to Thailand.

The most significant short-term ‘natural’ climate variation is the El Niño. Rainfall and temperature changes seen in El Niño events have been linked to epidemics of several tropical diseases. The 1997–98 El Niño event raised winter temperatures to 5°C above average in Lima, Peru, more than doubling the number of daily hospital admissions for diarrhoea.

Knowing when El Niño is due can enable countries to prepare for its impact. People can protect themselves from its direct effects, such as storms. In addition, countries such as Botswana now know that as simple a measure as sea surface temperature, through its effects on rainfall, will have a major impact on the spread of malaria, giving them several months’ advance warning of a possible epidemic.

Lead image:

Patients affected by Dengue fever and malaria rest in the Mahidol Tropical Medicine Hospital outside Bangkok (2012).

Sanofi Pasteur/Patrick de Noirmont/Flickr CC BY NC ND


About this resource

This resource was first published in ‘Health and Climate Change’ in January 2009 and reviewed and updated in September 2014.

Statistics and maths, Microbiology, Ecology and environment, Health, infection and disease
Health and Climate Change
Education levels:
14–16, 16–19, Continuing professional development