Climate change: Warmer... but why? | Upsetting the balance | Mammals on the move
Connecting climate and disease | How do sea shells record temperature change?
Taking Earth's temperature


Are global warming and climate variability contributing to the spread and burden of disease?

That's the concern of Mercedes Pascual, U-M Associate Professor of Ecology and Evolutionary Biology. Professor Pascual takes an ecological approach to understanding human disease patterns.



Photo courtesy of International Center for Diarrhoeal Disease Research in Bangladesh

Cholera, a world-wide health problem

This photo shows a child being carried who is ill with cholera. This disease is a serious health problem in many parts of the world, especially in underdeveloped third-world nations where health care is scarce and sanitation is poor. Cholera causes vomiting and diarrhea, which can lead to severe dehydration and even death, if patients are not treated promptly. Infection with a bacterium called Vibrio cholerae causes the disease.


This is a greatly enlarged image of the cholera-causing bacterium Vibrio cholerae. It takes up residence in the intestines, causing the symptoms associated with
this disease.

Copyright: Dennis Kunkel Microscopy, Inc.


Climate and cholera

In one of Professor Pascual’s research projects, she and collaborators in Barcelona, London, and Bangladesh found evidence that a phenomenon called the El Niño-Southern Oscillation (ENSO), which is a major source of climate variability from year to year, influences cycles of cholera in Bangladesh. El Niño is an abnormal, sustained warming of ocean surface waters in the eastern tropical Pacific Ocean.

In this false-color photograph of Earth taken by the orbiting TOPEX/Poseidon satellite in October 1997, warm water is shown in white. The large, white area represents El Niño– an abnormally large mass of warm water, 30 times larger than all the Great Lakes, flowing from the eastern Pacific toward the Americas.

The ocean's changes affect the atmosphere. Hot, humid air over the oceans fuels tropical thunderstorms, which move eastward along with the Pacific's warmest water. The atmosphere also responds by producing patterns of high and low pressure, which can affect weather in other parts of the world.



The connection:
How does climate exert its
influence on cholera?

Because the bacterium that causes cholera lives in brackish water and thrives in warm temperatures, it may be especially sensitive to climate patterns. People usually get the disease by eating or drinking contaminated food or water, which is more likely to happen in warmer weather or after natural disasters, such as floods. Recent research shows that rainfall and associated flooding following El Niño events can drive increases in cholera cases in Bangladesh. This aspect of the connection between warming temperatures in the Pacific during an El Niño, and the regional weather in Bangladesh that affects cholera, is currently under investigation.


What’s the big deal?

Over the last three decades of the 20th century, scientists have noted a tendency toward warmer ENSO events, in conjunction with global warming. With the likelihood that ENSO will become stronger and more variable in coming years due to climate change, Professor Pascual says, “Understanding its connection to human disease will be increasingly important. In addition, the susceptibility of cholera to climatic factors raises concerns about the future effects of global warming itself, as environmental conditions might become more suitable for the more sustained spread of this, and other diseases.”


Climate change: Warmer... but why? | Upsetting the balance | Mammals on the move
Connecting climate and disease | How do sea shells record temperature change?
Taking Earth's temperature