Usually, when we think about global climate change, we thing about things like the melting
Arctic and
Antarctic, the recent
heatwaves in Europe,
rising seas, and of course the
main cause of global warming, among other things.
As alarming as those symptoms of climate change are, there's one subject that has been somewhat neglected in the mainstream discussion of global climate change: the emergence, and re-emergence, of a variety of serious human infectious diseases, as mentioned in a presentation given at the American Association for the Advancement of Science (AAAS) conference this week in Washington, D.C.
So, I did some research on the internets, and found that among the many diseases mentioned, one showed up over and over again. A pretty scary one.
It has to do with a mouse, El Niño events, and my home state.
Intrigued? Turn the page.
Flashback to 1993
In May 1993, there was an outbreak of an acute illness in the Four Corners area of the southwest (map - I'm from New Mexico). The illness was characterized by a high fever, muscle aches, headaches, chills, and stomach aches, progressing to shortness of breath caused by the lungs filling with fluid. Of the 24 people infected, half of them died. Tests showed that the disease was caused by a previously unknown hantavirus. The disease was therefore dubbed "hantavirus pulmonary syndrome" or HPS.
Researchers were able to determine that the virus was carried by deer mice (Peromyscus maniculatus), who excrete it in their urine and feces. All the people who contracted HPS lived in areas where they were exposed to the mice. The virus was named the Sin Nombre virus. So, now, in addition to bubonic plague, New Mexicans had another disease to worry about.
Unfortunately, to this date, there is no cure for HPS. However, if the disease is diagnosed in time, patients' blood can be oxygenated via extra-corporeal membrane oxygenation. The biggest spike in cases was in 1993 (click here - pdf).
Disease outbreak and climate change
After the HPS outbreak in 1993, multiple studies were done to determine why it was so bad that particular year. To make a long story short, you can blame the increased precipitation from the 1992 El Niño/Southern Oscillation (ENSO). The World Health Organization lists a number of other diseases that are affected by ENSO; that fact sheet also mentions that scientists are beginning to think that global warming will affect the frequency and intensity of ENSO events (as predicted by this model, among other studies).
Most damning of all is this study, which shows the increased relationship between ENSO and cholera in Bangladesh. In fact, it's probably the first piece of evidence that global warming over the last century is affecting human disease. In a way, it's possible that disease outbreaks can be seen as evidence of global warming.
Back to the Sin Nombre virus
DISCLAIMER: I am not a climate scientist, nor am I an epidemiologist. However, something on the CDC hantavirus website caught my interest. It's refering to the Four Corners cases in 1993:
But why this sudden cluster of cases? The key answer to this question is that, during this period, there were suddenly many more mice than usual. The Four Corners area had been in a drought for several years. Then, in early 1993, heavy snows and rainfall helped drought-stricken plants and animals to revive and grow in larger-than-usual numbers. The area's deer mice had plenty to eat, and as a result they reproduced so rapidly that there were ten times more mice in May 1993 than there had been in May of 1992. With so many mice, it was more likely that mice and humans would come into contact with one another, and thus more likely that the hantavirus carried by the mice would be transmitted to humans.
Anyone from New Mexico (or who has been there recently) has probably heard us complaining about the drought we, and the rest of the southwest, have been in for six years. But now we're having an exceptionally wet, warm spring, with precipitation in the northwest corner of the state between 136%-287% above normal (pdf). I just hope we don't end up with too many happy deer mice.
Conclusion
The bad news: Global climate change doesn't just mean melting polar ice caps, rising tides, warmer oceans, etc. It also means that there are going to be some serious problems with human diseases and other health problems.
The good news: We can do something about this. The coming disease crisis is something we can prepare for, and at least in the case of New Mexico, health care workers know how to deal with hantavirus cases (as well as plague).
Cross-posted on Liberal Street Fight.