Climate change and infectious diseases Infectious diseases node Adaptation Research Network: human health David Harley National Centre for Epidemiology and Population Health & ANU Medical School
Effects of climate change on infectious disease Individual (and population risk) for infectious disease is determined by: 1. Host 2. Agent 3. Environment Climate is one component of environment but has impacts on host and agent
Effects of climate change on infectious disease Climate determines the boundaries within which infectious diseases may occur, but Other environmental influences may increase (e.g. water storage and mosquito breeding) or decrease (e.g. surveillance, vector control, treatment) risk, sometimes to a greater extent than climate
Effects of climate change on infectious disease Host human physiology, behaviour, perhaps immune response etc. Agent reproduction rates, extrinsic incubation period for arthropod-borne diseases etc. Environment built environment, water storage, distribution of insect vectors etc.
Ross River Virus, Rainfall and Mosquito Density: Queensland, 1998-2001 Rainfall, 18 mosquito density and RRV in Brisbane 900 16 14 12 10 18 16 14 12 10 8 6 4 Incidence rate of RRV (1/100,000) RRV Incidence (per 10 5 ) 2 Nov-98 Nov-99 Jan-99 0 Incidence rate of RRV Ross River Virus, Rainfall Rainfall and Mosquito Density: Queensland Mosquito density Mar-99 Jan-00 May-99 Jul-99 May-00 Sep-99 Nov-99 Jan-00 Mar-00 Nov-00 May-00 Jul-00 Jan-01 Sep-00 Mar-01 Nov-00 May-01 Jan-01 Mar-01 May-01 Sep-01 Jul-01 Sep-01 Nov-01 Nov-01 Year Year 900 800 700 Mosquito density/rainfall (mm) Mosquito Density / Rainfall (mm) 8 6 4 2 0 Positive relationship Incidence between rate of rainfall RRV and Mosquito Density Rainfall RRV Disease 600 400 500 400 Incidence rate of RRV (1/100,000) 300 200 100 Tong et al, date? Tong, McMichael, et Tong al, et 2005 al 0 Nov-98 Jan-99 Mar-99 May-99 Jul-99 Sep-99 Mar-00 Jul-00 Sep-00 Jul-01 Year 800 Mosquito Mosquito Density density/rainfall / Rainfall (mm) (mm) mosquito density, Rainfall with increased density after lag of 1-2 months followed by RRV Mosquito density outbreaks. Mosquito Density Rainfall RRV Disease 700 600 500 300 200 RRV Incidence (per 10 5 ) 100 0
Dengue in North Queensland, by Serotype, 1954-2003 Serotype Townsville, Charters Towers & Cairns Townsville Torres Strait Islands
Historical extent of dengue further South than currently Dengue Projected increase in extent of dengue transmission in Australia on the basis of a global transmission model (Hales, 2002) Sources: Russell RC, et al. Dengue and climate change in Australia - predictions for the future should incorporate knowledge from the past. Med J Aust 2009;190:265-268 & McMichael A. et al. Human Health and Climate Change in Oceania: A Risk Assessment. Canberra: Commonwealth of Australia, 2003.
Aedes aegypti Source: Kearney, M. et al. Integrating biophysical models and evolutionary theory to predict climatic impacts on species ranges: the dengue mosquito Aedes aegypti in Australia Functional Ecology 2009:23;528-538.
Aedes aegypti Incorporation of biophysical properties of breeding containers with evolutionary potential to make projections A need for collaboration and the incorporation of such strategies with epidemiological approaches Source: Kearney, M. et al. Integrating biophysical models and evolutionary theory to predict climatic impacts on species ranges: the dengue mosquito Aedes aegypti in Australia Functional Ecology 2009:23;528-538.
Model-fitted predictions of monthly Salmonellosis case counts in relation to monthly av. temperature in five Australian cities, 1991-2001 Salmonella case count 100 90 80 70 60 50 40 30 20 10 0 Sydney Melbourne Brisbane Perth Adelaide 1 o C rise 10% incr 5 o C rise 60% incr 9 10111213141516171819202122232425262728 Average temperature o C, previous month D Souza et al., 2003
Infectious diseases node: some activities Preparation of papers adaptation to climate change and infectious diseases ANZJPH & discussion paper (Harley, Tong, Bi, Swaminathan, Williams) Grants dengue (Harley, Ritchie, Williams, Dear, McMichael) & Ross River virus (Tong, Harley and others) (Adaptation plan for climate change and health in Cambodia Harley, Swaminathan and others)
Adaptation to infectious diseases under climate change Adaptation research for policy: Bringing together different professional groupings in cooperative research Determining priority, relative to other health impacts, and impacts outside the health sector Projections of future incidence improved modelling, reduce concentration on vector-borne disease Adapting surveillance Planning for changed treatment needs (primary, secondary and tertiary care education, resources etc.)