Climate change and disease

Posted: 28 September 2007

Changes in climate are likely to affect the incidence of diseases such as malaria, dengue and schistosomiasis by extending the range of their vector insects. A temperature rise of 1-2 degrees centigrade could result in an increase of the population at risk of contracting dengue by several hundred million, with 20,000-30,000 more dengue deaths a year by 2050.

  • Climatic changes over recent decades have probably already affected some health outcomes. The World Health Organisation estimated, in its World Health Report 2002, that climate change was estimated to be responsible in 2000 for approximately 2.4 per cent of worldwide diarrhoea, and 6 per cent of malaria in some middle-income countries.

  • WHO believes that the first detectable changes in human health may well be alterations in the geographic range (latitude and altitude) and seasonality of certain infectious diseases - including vector-borne infections such as malaria and dengue fever, and food-borne infections (e.g. salmonellosis) which peak in the warmer months.

Malaria mosquito
Malaria mosquito
Climate change may cause malaria-carrying mosquitoes to migrate. Photo credit: Population Media
  • By 2100, climate change could have increased substantially the proportion of the world's population living in potential malaria transmission zones. A global mean temperature rise of 3° Celsius by 2100 would double the epidemic potential of mosquito populations in tropical regions and increase it in temperate regions more than 10 times.

  • Irrespective of climate change effects, if current trends in greenhouse gas emission continue, some scientists believe there could be 700,000 extra avoidable deaths annually because of additional exposure to atmospheric particulate matter produced by the burning of fossil fuels, with 80 per cent of these deaths occurring in developing countries.

  • By 2050, many cities could be experiencing several thousand extra heat-related deaths annually, irrespective of any increase due to population growth.

  • Additional extreme weather events, such as floods, storms and droughts could result in greater risk of death, injury and starvation and increased incidence of psychological and social disorders.

  • Increased exposure to ultraviolet radiation due to atmospheric ozone depletion could lead to an increase in skin cancers, cataracts and possibly suppression of the body's immune system.

  • Sea level rise could result in displacement, loss of agricultural land and some fisheries, freshwater salinisation and social disruption, all of which could affect health status.

  • The El Niño cycle, which may be affected by global warming, is associated with increased risks of some of the diseases transmitted by mosquitoes, such as malaria, dengue and Rift Valley fever. Malaria transmission is particularly sensitive to weather conditions. In dry climates, heavy rainfall can create puddles that provide good breeding conditions for mosquitoes. In very humid climates, droughts may turn rivers into strings of pools, preferred breeding sites of other types of mosquito.