Thomas Gale Moore
Senior Fellow
Hoover Institution
Stanford University
Vocal advocates of acting now to head off the possibility of global warming, from Vice-President Al Gore on down, having failed to make the case that climate change would cause noticeable economic costs, are attempting to scare the public through allegations that a warmer climate would bring death and disease. The latest manifestation of this fearmongering is a curious article in Science taken from a modified text of Rita Colwell's Presidential address to the AAAS's 1996 annual meeting. This address presents a studious analysis of cholera and its recent resurgence in the Americas. What is most singular is not what is in Dr. Colwell's report, but what she does not mention.
Despite its title "Global Climate and Infectious Disease: the Cholera Paradigm," climate change is hardly broached, and the one reference to it comes in connection with malaria, not cholera. Certainly Cowell makes no effort to tie global warming to the spread of cholera. Moreover, in a section strangely entitled "Global Climate, Global Change, and Human Health," the word "climate" does not appear; nor do the words: "warmer," "temperature," or "global"! Also puzzling for such a careful exposition is the absence of any reference to the role that the U.S. Environmental Protection Agency may have had in creating the conditions leading to the explosion of cholera in Peru in 1991. But more on that later.
First a few dry facts about cholera, an infectious disease caused by the Vibrio cholerae, a bacterium that can bring on diarrhea, vomiting, and leg cramps. Without treatment, a person can rapidly lose body fluids, become dehydrated and go into shock. Death can come quickly. Treatment is simple, the replacement of the fluids and salts with an oral rehydration solution of sugar and salts mixed with water. Fewer than one percent of those who get cholera die.
Cholera cannot be caught from others but comes from ingesting food or water that contain the bacterium. Eating tainted shellfish, raw or undercooked fish, raw vegetables, or unpeeled fruits can lead to infection. Drinking unpurified water can be dangerous as well. The bacterium thrives in brackish warm water but can survive, in a dormant state, both colder water and changes in salinity. V. cholerae is also associated with zooplankton, shellfish, and fish. It often colonizes copepods, minute marine crustaceans. Ocean currents and tidal movements can sweep the bacterium riding on copepods along coasts and up estuaries where V. cholerae can remain dormant until conditions are ripe for it to multiply.
In 1817, the British first identified this dreaded disease in Calcutta, from where it spread throughout India, Nepal, and Afghanistan. Ships carried it into Asia, Arabia, and to the ports of Africa. It reached Moscow, its first port of call in Europe, in 1830, creating panic as locals fled the city. From there it traveled to Poland, Germany and England. In the decade after it first appeared in Europe, it killed tens of thousands in Paris, London, and Stockholm. It reached North America in 1832, appearing first in New York and Philadelphia, then spreading along the coast to New Orleans. In the same year, the disease killed over 2200 people in Quebec. Apparently cholera is not a tropical disease; it can kill and sicken in any climate, although in high latitudes it may do so only in the summer.
Prior to the current outbreak, the world suffered six cholera pandemics. By the end of the nineteenth century, however, Europe and North America were free of the disease. The solution was simple: filtration and chlorination of the water supply. Filtering alone reduces not only the spread of cholera but cuts typhoid significantly. Combining filtration with chlorine eliminates waterborne diseases. A warmer climate, if it were to occur, would not reduce the effectiveness of these water purification measures.
In January 1991, after many disease free decades, cholera began sickening villagers in Chancay, Peru, a port less than 40 miles north of Lima. From there it spread rapidly up and down the coast. From that outbreak to the end of 1995, Latin America has reported over 1 million cases -- many went unreported -- and 11,000 deaths. The illness spread from Peru, to Ecuador, Colombia, then Brazil. Eight months after appearing in Peru, it reached Bolivia. By the end of 1992, virtually all of South and Central America, from Mexico to Argentina had confirmed cases. Cholera has also entered the United States; however, with the exception of a few cases brought on from eating raw tainted shellfish, virtually all cases were contracted abroad. Seventy-five cases, nearly half of the total 160 reported to the CDC between 1992 and 1994, originated on a single flight from Lima in 1992!
What went wrong to bring an end to Latin America's 100 years of freedom from cholera? Rita Colwell theorizes that an El Niño led to a plankton bloom that multiplied the hosts of V. cholerae. But El Niños have been occurring with some regularity for many years without producing a cholera epidemic. As the chart shows the coast of Peru in 1991 was not even particular warm compared to a number of other years. Even if El Niño were in part the culprit, the basic cause lies elsewhere. Based on U.S. Environmental Protection Agency studies showing that chlorine might create a slight cancer risk, authorities in Peru had decided not to chlorinate their country's drinking water. Perhaps they also thought they would save money. Chlorination, however, is the single most effective preventive of cholera and other waterborne diseases. After the fiasco in Peru, the E.P.A. determined in 1992 that there was no demonstable link between chlorinated drinking water and cancer. It was too late; the harm had been done. Peru's misplaced environmentalism led to more than 300,000 victims in that country alone.
Cholera is a disease of poverty, crowding, and unsanitary conditions. A warmer climate will not carry this disease to affluent countries; but in the Third-World, economic growth can bring freedom from this and many other diseases. We should not impose costs on us or on others that would reduce the resources needed to bring clean water and good sanitation to Latin America, Africa and Asia.
References:
Rita R. Colwell. "Global Climate and Infectious Disease: The Cholera Paradigm," Science 274 (20 December 1996): 2025-2031.
Arno Karlen. Man and Microbes New York: Simon & Schuster 1995.
Barbara E. Mahon, et al. "Reported Cholera in the United States, 1992-1994," JAMA (July 24/31, 1996): 307-312.
Pan American Health Organization, Comunicable Disease: Cholera Surveillance Information.
Christopher Anderson. "Cholera Epidemic Traced to Risk Miscalculation," Nature 354 (28 November 1991): 255.