Climate change is affecting our health- impacts & health risks

Climate change is the “biggest global health threat of the 21st century, many observers expect that the earth will warm to at least 2ºC (3.6ºF) over the preindustrial average; rainfall patterns will change; extreme weather events will become more frequent; sea levels will rise, with increased flooding in coastal areas; and so forth. Such changes may have serious repercussions for children and families worldwide.

Climate  change entails a wide variety of public health risks, authorities, and other stakeholders thus need to  understand the current and projected impacts of climate change and their implications for health to prepare  and implement a variety of responses to ensure an optimal level of adaptation.

Examples of such  responses include early warning systems, emergency management plans and provisions, and health  systems strengthening; other preventive measures include safer housing, flood protection, vector control, and improved surveillance.

Climate change and human health

Climate change is expected to cause approximately 250 000, additional deaths per year between 2030 and 2050, and approximately 87 million people were displaced due to extreme weather events between  2008 and 2011.

(WHO) estimates that every year about 150 000 deaths occur worldwide in low-income countries due to adverse effects of climate change, such as malnutrition, floods, diarrheal diseases, and malaria. FAO estimates that by 2030, up to 122 million more people could be forced into extreme poverty because of climate change.

Direct health effects will be temperature-related illness and death, extreme weather-related health effects, and airborne-related health effects. Indirect health effects are water and food-borne, vector-borne, and rodent-borne diseases, food and water shortage, and nutritional and mental health effects. Excess mortality due to heatwaves is greatest in  the elderly and those with low immunity.

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How does climate change impact our health?

This mortality occurs because of CVD or cerebrovascular, or  respiratory diseases. Winter mortality was reported to be 10-25 % higher than those in summer, due  to CVD, circulatory and respiratory diseases, and influenza outbreaks.

In terms of the Burden of disease,  measured by DALYs, climate change is estimated to have caused the loss of over 150,000 lives and  5,500,000 DALYs (0.3% of deaths and 0.4% of DALYs, respectively) ( WHO, 2013). The Middle East is going to experience climate change threatening basic life, due to reduced surface water hitting agriculture and resulting in crop failure which might lead to starvation and poverty.  

Lack of available drinking water will increase cholera and other waterborne diseases. The government could respond by importing more water at a financial cost but also an environmental one, as it requires transport, causing again the release of CO₂.

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UAE has one of the highest levels of GHG emissions per capita, however, only limited impacts on infectious and diarrheal diseases in the UAE due to relatively low baseline levels of these climate-sensitive diseases. The major impacts of climate change in the UAE are expected to be increased heat stress.    

Climate change has enormous and diverse effects on human health. Rises in temperature and sea level and extreme weather events such as floods cause water logging and contamination, which in turn exacerbate diarrheal diseases. Vector-borne diseases and other communicable diseases will be the result of climate change. Poor and poorer nations will be more impacted due to fragile health systems and resources. 

Climate change & vector-borne diseases

Higher temperatures in combination with conducive patterns of rainfall and surface water, climate variability, and poor public health infrastructure would alter the geographical range and seasonality of the distribution of vector organisms (e.g., malarial mosquitoes)(WHO,1998).

Alternatively, a change in the ecology of the natural predators may affect mosquito vector dynamics; mosquito populations recover more quickly than their predator populations following a dry year.

Temperature-related changes in the life-cycle dynamics of both the vector species and the pathogenic organisms (flukes, protozoa, bacteria, and viruses) would increase the potential transmission of many vector-borne diseases such as malaria (mosquito), dengue fever (mosquito) and leishmaniasis (sand-fly)—although schistosomiasis (water snail) may undergo a net decrease in response to climate change.

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How temperature affects vector population

• Temperature reduces the time taken for vector populations to breed.  
• Increases in temperature also decrease the incubation period of the pathogen (e.g. malaria parasite,  dengue or yellow fever virus) meaning that vectors become infectious more quickly
• However, hot, dry conditions can reduce the lifetime of mosquitoes.  
• Temperature also may affect the behavior of the vector and human populations, affecting the probability of transmission.
• Warmer temperatures tend to increase the biting behavior of the vector and produce smaller adults which  may require multiple blood meals to reproduce

Climate change & transmission of vector-borne diseases

• Survival and reproduction rate of the vector 
• Time of year and level of vector activity, specifically the biting rate
• Rate of development and reproduction of the pathogen within the vector

The most influential climatic factors for vector-borne diseases

•  Temperature and precipitation  
• Sea level elevation
• Wind and daylight duration are additional important considerations
• Extreme temperatures often are lethal to the survival of disease-causing pathogens but incremental changes in temperature may exert varying effects.  
• A vector lives in an environment of low mean temperature, a small increase in temperature may result in increased development, incubation, and replication of the pathogen 
• The temperature may modify the growth of disease-carrying vectors by altering their biting rates, as well as affect vector population dynamics and alter the rate at which they contact humans. Finally, a shift  in temperature regime can alter the length of the transmission season 
• Disease-carrying vectors may adapt to changes in temperature by changing geographical distribution.  An emergence of malaria in the cooler climates of the African highlands may be a result of the  mosquito vector shifting habitats to cope with increased ambient air temperatures 
• Another possibility is that vectors undergo an evolutionary response to adapt to increasing temperatures.

Types of vector-borne diseases influenced by climate change

• Ticks, their animal hosts (deer), tick-borne diseases ex; encephalitis
•  Lyme disease is caused by bacteria “borrelia type” spread by ticks
•  West Nile virus has no medications or vaccines to prevent it, recovery takes weeks or  months
• Dengue
• Leishmaniasis

“Climate change scenarios over the coming century would cause a small net increase in the proportion of the world population living in regions of potential transmission of malaria and dengue”

Drought in the previous years has been identified as a factor contributing to increased malaria  mortality. There are several possible reasons for this relationship. Drought-related malnutrition may  increase an individual’s susceptibility to infection