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Infectious, Vector-Borne and Respiratory Disease and Drought

Infectious Disease- One of the factors involved in an increase of infectious disease during times of drought is a decrease in personal hygiene. Individuals may respond to a real or perceived need to save water by reducing or eliminating hand-washing, showering, and the washing of clothing and eating utensils. This increases the risks of them contracting, as well as transmitting, infectious diseases, especially acute respiratory and gastrointestinal diseases that are spread by direct contact.

For rural populations in dry countries like Sudan, drought can sometimes lead to devastating cholera outbreaks. When the wet season arrives, torrential downpours become common. However, with the ground so dry from drought season, the water can not be readily absorbed into the soil. Instead, it lays on top of the dirt and areas are quickly flooded. This alone can be dangerous. In refugee camps and heavily-populated areas, the vehicles that deliver safe drinking water to different parts of the community are sometimes unable to drive through the floods, forcing people in the camps to resort to drinking the unsafe floodwaters that easily carry disease such as cholera. Even before the floodwaters of the rainy season arrive, as drought dries up rivers that flow to and from lakes, pools of water become stagnant. In this state, both algae and parasites multiply, poisoning the water supply.

Vector-Borne Disease- Droughts affect mosquito activity worldwide. In the beginning of drought season in sub-Saharan Africa, mosquito activity is initially increased as small rivers, ponds and lakes shrink, resulting in shallow, warm, stagnant pools of water. As drought continues, mosquito activity decreases. Although less mosquitoes results in less infections initially, in the longer term it increases the effects of malaria. Once a person contracts malaria, he or she is less likely to become infected again due to antibodies. As mosquito activity decreases, the population of non-infected and therefore non-immune people increases (including babies and children, the group most likely to die from malaria). Eventually, when the drought breaks, there is a large number of susceptible hosts now vulnerable to infection. A similar pattern is true, too, for West Nile Disease-carrying mosquitoes in North America.

In times of low water supply, mice and deer tend to wander closer to human homes and yards in search of hydration. This increases the risk of nearby humans contracting Lyme Disease, as the deer ticks which carry the disease live on both mice and deer.

Respiratory Disease- Heat waves that accompany droughts have a tendency to incite wildfires, which heavily pollutes the air for hundreds, or even thousands, of miles in every direction. The particulate matter floating in the air has the serious potential to aggravate the lining of the respiratory tract, especially in people who already suffer from respiratory diseases like asthma and bronchitis. Dust storms that blow from parched land, much more likely to occur in times of severe drought, do the same. Though much of the particulate matter in the air during dust storms is too course to reach much of the respiratory tract, some is fine enough to make its way through the bronchioles that attach to the lungs, irritating the lining and causing inflammation.

Mental Health- Rates of suicide in Australian farmers are higher than the national average, but during times of drought these rates increase. This is due to a number of reasons. Firstly, there is intense financial pressure on farmers. Farmers also tend to be of lower socio-economic standing and so have less of a financial reserve. A few years of decreased production can be quite devastating. This pressure can lead to high rates of depression and suicide. There are also less medical, let alone mental health, resources available in rural communities, making it difficult for this group to access resources such as counselling. For older farmers, there are the added stresses of aging and coping with rapid agricultural and societal change, including new procedural demands from governments. Studies have also shown increased rates of substance use by farmers during drought, which can have an impact on individual safety (especially when operating heavy machinery), as well as on family and community health.

Drinking Water and Drought

In rural Africa and the Middle East, when droughts dry up the regular water supply, rural and impoverished families are forced to resort to drinking the dirty, sediment-and-parasite-laden water that sits in puddles and small pools on the surface of the earth. Many are aware of the presence of contamination, but will drink from these sources nonetheless in order to avoid dying of dehydration. It has been estimated that up to 80% of human illness in the world can be attributed to contaminated water.

When there is an adequate amount of drinking water, humans drink from different sources than their livestock. However, when drought occurs and drinking water disappears, catchment areas such as streams and depressions in the ground where water gathers are often shared between people and the livestock they depend on for financial and nutritional support, and this is when humans can fall seriously ill. Although some diseases that are transferred to humans can be prevented by boiling the water, many people, living on just a litre or two of water per day, refuse to boil, as it loses a certain percentage of the water to steam. The sharing of water between livestock and humans is one of the most common factors in the transmission of non-tuberulosis mycobacteria (NTM). NTM is carried in cattle and pig feces, and if this contaminates the drinking water supply, it can result in pulmonary disease, disseminated disease or localized lesions in humans with both compromised and competent immune systems.

During drought, water supplies are even more susceptible to harmful algal blooms and microorganisms. Algal blooms increase water turbidity, suffocating aquatic plants, and can deplete oxygen, killing fish. Some kinds of blue-green algae create neurotoxins, hepatoxins, cytotoxins or endotoxins that can cause serious and sometimes fatal neurological, liver and digestive diseases in humans. Cyanobacteria grow best in warmer temperatures (especially above 25 degrees Celcius), and so areas of the world that are experiencing general warming as a result of climate change are also experiencing harmful algal blooms more frequently and for longer periods of time. During times of intense precipitation (such as during the “wet season” in much of the tropical and sub-tropical world, including Australia and Panama), nutrients that cyanobacteria depend on are carried from groundwater and the earth’s surface into bodies of water. As drought begins and these bodies gradually dry up, the nutrients are concentrated, providing the perfect opportunity for algal blooms.

Low crop yields, food prices and health associated with drought

Arguably one of the worst effects that drought has directly on human health is the destruction of food supply. Farmers who depend on weather to water their crops lose tons of crops per year due to drought. Plant growth is severely stunted without adequate water, and plant resistance mechanisms to fungi and insects weaken like human immune systems. The expression of genes is altered by increased temperatures, which can also affect a plant’s resistance mechanisms. One example is wheat, which has the ability to express genes that make it resistant to leaf and stem rusts, and to the Hessian fly; its resistance declines with increasing temperatures. A number of other factors associated with lack of water may actually attract pestilent insects, as well- some studies have shown that many insects are attracted to yellow hues, including the yellowing leaves of drought-stressed plants. During times of mild drought is when conditions are most suitable to insect infestation in crops; once the plants become too weakened, they lack the nutrients necessary to keep the insects healthy. This means that even a relatively short, mild drought may cause enormous damage- even though the drought on its own may not be enough to kill a significant portion of the crops, once the plants become weakened, they are at higher risk of becoming infested.

The results of the loss of crop yields affect everyone, but they can be felt most by the poorest people in the world. As supplies of corn, flour and vegetables decline, world food prices are driven up. Malnutrition rates in poor areas of the world skyrocket, and with this, dozens of associated diseases and health problems. Immune function decreases, so mortality rates due to infectious and other diseases climb. For those whose incomes were affected by droughts (namely agriculturalists and pastoralists), and for those who can barely afford the increased food prices, the cost to see a doctor or visit a clinic can simply be out of reach. Without treatment, some of these diseases can hinder one’s ability to work, decreasing future opportunities for income and perpetuating the vicious cycle of poverty.

Cholera

Cholera is spread by drinking water that is contaminated with the Vibrio cholerae bacterium. Cholera epidemics have been noted to occur often during El Nino, the climate event that increases the temperatures of near-shore coastal waters, showing a link between temperature and cholera spread. V. cholerae exist in the ocean and in waterways in a hardy, dormant state and can remain in that state for years. Studies have shown that when seawater warms, nitrogen and phosphorus levels increase and dormant cholera bacteria become active and infectious. Then, when monsoons and hurricanes arrive, they sweep over waterways that are used by humans, filling rivers, lakes and ponds used for cleaning and for drinking water with a rush of the now-active bacteria.