South-East Asia Regional Conference on Epidemiology

1.1 Thermal extremes
<strong>South</strong>-<strong>East</strong> <strong>Asia</strong> <strong>Regional</strong> <strong>Conference</strong> on Epidemiology | 237
The increased frequency and intensity of extreme temperatures may have direct impacts on human
health in terms of thermal stresses, such as hypothermia, influenza, cardiovascular and respiratory
diseases, heat exhaustion, heat cramps, dehydration and many others (7, 8). These may lead to higher
levels of urban air pollution and humidity or exacerbate pre-existing respiratory problems (9-11).
It has been postulated that the increase in heat-related stresses may be compensated by a decrease in
cold-related illnesses in the winter season, leading to an overall positive impact (12-14). These effects
are nevertheless under debate, as the projected mortality for winter diseases might be underestimated
if the effect of influenza is not considered (15). Further research is needed in this context to identify
the impacts under different climatic conditions and socioeconomic scenarios.
1.2 Air pollutants and aero-allergens
Weather conditions can affect the transportation of airborne pollutants (reduced atmospheric dispersion
and diffusion) and production of certain kinds of pollen. Asthma, allergies and other acute and chronic
respiratory disorders are generally associated with such episodes of air pollution (16,17). Increased
temperature is also expected to increase the frequency and/or intensity of forest and range-land fires.
The increased particulate exposure due to the resulting smoke and particulate matter may lead to
respiratory and cardiovascular conditions (18).
1.3 Extreme events
According to the IPCC Fourth Assessment Report, any regional increases in climate extremes (e.g.
storms, floods, cyclones, droughts) associated with climate change would cause deaths and injuries,
population displacement, adverse effects on food production, freshwater availability and quality, and
would increase the risks of infectious diseases, particularly in low-income countries (19).
The health effects of flooding include deaths and injuries (direct impact) as well as indirect effects
such as mental health problems (anxiety and depression) and increased water-borne diseases (e.g.
diarrhoea, cholera, typhoid) due to water contamination (20, 21). Unsafe sanitary conditions and
decreased water accessibility further increase the chances of transmission of water-borne infections.
Crowding, common in populations displaced by climatic disasters like floods, can further facilitate
the transmission of communicable diseases (22). Extreme events of weather can also severely disrupt
the public health care facilities as well as emergency support services. It can temporarily lead to
suspension of disease control programmes due to inaccessibility of the affected region or due to
economic crisis arising after an event of a climatic disaster or epidemic. Of particular concern is the
impact of sea-level rise, especially in the coastal and low-lying areas where population displacement
and mass migration may impact the socioeconomic conditions of both the affected region as well as
the region to which the migration takes place (23). Drought events may cause increased malnutrition
and undernutrition due to loss in agricultural production and increased infectious and respiratory
diseases (24).
1.4 Infectious diseases
Other indirect impacts of changes in weather patterns include variation in the geographical and
seasonal distribution of vector-borne diseases (25-28). The risk of malaria might increase in some
regions in central <strong>Asia</strong> and India (29), while in other areas (Central America and Amazon) the
transmission could decrease because of reduced rainfall. Some regions are expected to have a longer
transmission season, with important implications for vector control programmes. Populations at the