SEATTLE — Cholera is not caused by poor sanitation alone. Recent research reveals that complex environmental factors can also intensify the severity and breadth of the disease.
With this understanding, researchers conclude that climate change can increase the incidence of cholera. In order to address this reality, they have developed tools to help mitigate an outbreak before it even begins.
Cholera is a waterborne disease, caused by a single-celled bacterium called vibrio cholerae. It is native to rivers, estuaries and coastlines, and is most prevalent around the Bay of Bengal, Africa and coastal Latin America.
If contaminated water or food is ingested, cholera infects the small intestine, resulting in diarrhea, vomiting, fever and life-threatening dehydration. According to the World Health Organization, the bacteria takes up to 142,000 lives per year.
Despite its deadly human impact, the bacteria is a vital aspect of marine ecosystem health. Vibrio cholerae recycles vast amounts of oceanic carbon by breaking down the chitin in the exoskeletons of arthropods. Due to this critical ecological role, the complete eradication of cholera is impossible.
Vibrio cholerae metabolizes chitin more effectively when it is attached to a kind of zooplankton, called a copepod, in a mutually beneficial relationship. The exoskeleton of the copepod protects the bacteria, allowing it to tolerate a wider pH range and providing a substrate for multiplication.
Climate change causes a number of environmental peculiarities, such as droughts, floods and warm, nutrient-rich waters. While these climatic events are already disastrous for humans, these conditions also further the growth of vibrio cholerae, which increases the incidence of cholera.
As sea surface temperatures rise, algal blooms increase. Zooplankton arrive to feed on the abundance of algae, carrying these bacteria with them. Climate change is bringing warmer waters to more regions of the world, making a greater extent of coastal developing countries susceptible to cholera endemics.
Droughts increase salinity, which helps vibrio cholerae to better attach to copepods and thrive. Floods help the bacteria widely distribute, increasing the risk of cholera – even in the areas that are farther inland.
A wide variety of climatic events helps the vibrio to grow and flourish. The frequency of these events is amplified due to climate change, so establishing and reinforcing sanitation systems in developing nations is essential in order to combat cholera.
Using remote sensing data in Bangladesh, researchers discovered that the risk of cholera increased two to four times in the six weeks following a 5 degree spike in sea surface temperature.
Strange climate patterns are only expected to increase in the coming years, so researchers at the University of Maryland are now using NASA satellite data to analyze the correlation between the incidence of cholera and climate and water cycles.
After identifying temperature, precipitation and groundwater levels as critical elements of cholera endemics, specialists are now able to predict future outbreaks months in advance, reducing the potential lethal impact of the disease.
Using sea surface temperature, height and salinity as variables, the timing, location and severity of a cholera outbreak can be specified, allowing for affected nations to prepare and receive aid.
Cholera can’t be fought with oral rehydration therapy and antibiotics alone. While these treatments are critical for immediate survival, cholera uniquely requires infrastructure development as its primary long-term cure.
As the climate is changing, developing nations receive unjust exposure to disease. To decrease the incidence of cholera, clean drinking water, quality sanitation systems, widespread vaccination, continued satellite warnings and a further understanding of microbial ecology is essential.
– Larkin Smith