Cholera Outbreaks and Ocean Climate

Rita R. Colwell Cholera Outbreaks and Ocean Climate W HAT I SHALL DO IN TH IS BRIEF PAPER, RATHER TH A N JUM P INTO THE ring w ith gloves to join th e debate on science and policy, is p u t a hum an face on one of the m ost serious issues we are discussing: the com plexity of clim ate change.' We need to understand very clearly that w hen one discusses, for example, clim ate and infectious disease, the problem is com plicated and the interactions involved are both m ultidisciplinary and interdisciplinary. The hum an perspective m ust be included if we are to com prehend fully the global effects of climate change. It would be useful to start not by belaboring points of conten­ tion but by indicating w here there is agreem ent. Everyone agrees that global w arm ing is occurring. Over the past few years, the highest average tem peratures in history have been recorded. No one argues that. The argum ent, of course, is w hether we are undergoing a natural cycle or anthropogenic-induced change. But, let us look at the fact th at the ocean surface annual tem peratures have increased. W arren W ashington speaks eloquently of his research at the National Center for A tm ospheric Research (NCAR) on th e dram atic changes such tem perature increases will invoke on sea surface levels (Washington, in press). My focus is on one aspect of global warming: hum an health and the w eather-related effects of clim ate change on infectious disease. The United States surgeon general’s report in 1950 declared the war social research Vol 73 : No 3 : Fall 2006 753 on infectious disease over because of the discoveries of m any power­ ful antibiotics. It was a prem ature declaration; infectious diseases are a moving target and rem ain very serious threats to the hum an race. Globally, acute respiratory infections, including pneum onia and influ­ enza (avian influenza is a loom ing threat), are the num ber one killer. However, for children under the age of five, diarrheal disease remains a m ajor killer, especially in developing countries. Cholera, a diarrheal disease, has been w ith us for a very long tim e, even being m entioned in ancient Sanskrit w ritings. A m edical textbook published in 1875 reported cholera to be a global pandem ic, consistently appearing in India, Bangladesh, Latin Am erica, and Africa. Today, cholera rem ains a serious problem . U ntil the nine­ teen th century, cholera was generally confined to the Indian subcon­ tinent, but it th en began to appear in Europe and the Americas as well. Since 1817, W estern m edical history describes seven global pandem ics o f cholera th a t have spread illness and death around the world. The second of these seven pandem ics reached the United States in 1832, traveling from New York to Philadelphia in a couple of weeks, and th en cases appeared along the A tlantic coast all the way to the Gulf of Mexico. In fact, W ashington, D.C. and New York, u n til 1900, saw frequent epidem ics of fevers, including typhoid, m alaria, and cholera. Cholera arose in epidem ic form in London in 1849, at a tim e w hen the germ theory of disease was being debated. John Snow, in that year, carried out the first published epidemiological study, charting cases of cholera in London. He concluded that the cholera cases clus­ tered around a well in central London w hen cholera was at its peak during the sum m er m onths. The epidemic abated in the September of 1849 but, as I will explain, the decline had to do w ith natural factors rather than the purported removal of the handle from the pum p by John Snow. In 1977, my cow orkers and I reported th at Vibrio cholerae, the causative agent of cholera, could be cultured from Chesapeake Bay 754 social research w ater samples. It was the first report of the isolation of the chol­ era vibrio from noncholera-endem ic geographical...