The Awful Diseases on the Way by Annie Sparrow
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Font Size: A A A The Awful Diseases on the Way Annie Sparrow JUNE 9, 2016 ISSUE Pandemic: Tracking Contagions, from Cholera to Ebola and Beyond by Sonia Shah Sarah Crichton Books/Farrar, Straus and Giroux, 271 pp., $26.00 Pandemics—the uncontrolled spread of highly contagious diseases across countries and continents—are a modern phenomenon. The word itself, a neologism from Greek words for “all” and “people,” has been used only since the mid-nineteenth century. Epidemics—localized outbreaks of diseases—have always been part of human history, but pandemics require a minimum density of population and an effective means of transport. Since “Spanish” flu burst from the trenches of World War I in 1918, infecting 20 percent of the world’s population and killing upward of 50 million people, fears of a similar pandemic have preoccupied public health practitioners, politicians, and philanthropists. World War II, in which the German army deliberately caused malaria epidemics and the Japanese Hosam Katan/Reuters experimented with anthrax and plague as biological A health worker marking a child who has been given a polio vaccination, Aleppo, Syria, weapons, created new fears. May 2014 In response, the US Centers for Disease Control (CDC), founded in 1946 to control malaria domestically, launched its Epidemic Intelligence Service in 1951 to defend against possible biological warfare, an odd emphasis given the uncontrolled polio epidemics raging in the 1940s and 1950s in the United States and Europe. But in the world of public health, the latest threat often takes precedence over the most prevalent. According to the doctor, writer, and philanthropist Larry Brilliant, “outbreaks are inevitable, pandemics are optional.” Brilliant, a well-known expert on global health, ought to know, since he has had much to do with smallpox eradication. Smallpox, arguably the worst disease in human history, caused half a billion deaths during the twentieth century alone. The strain called Variola major—the most lethal cause—killed one third of all infected and permanently scarred all survivors. In 1975, Rahima Banu, a two-year-old Bangladeshi girl, became the last case of V. major smallpox. Two years later, Ali, a twenty-three-year-old hospital cook in Somalia, became the last case of V. minor. Rahima and Ali survived. Smallpox did not. Forty years later, smallpox is still the only disease affecting humans ever to have been eradicated. (Rinderpest, a virus affecting cows—literally “cattle plague”—was eradicated in 2011.) There is optimism that polio and guinea worm may soon follow. Meanwhile, dozens of new infectious diseases have emerged, including the pathogens behind the twenty-first- century “pan-epidemics”—a term coined by Dr. Daniel Lucey to describe SARS, avian flu, swine flu, MERS, Ebola, and now Zika. The fear, fascination, and financial incentives that these new diseases create divert attention and resources from ancient diseases like cholera, malaria, and tuberculosis, which infect and kill far more people. Ebola has caused relatively few deaths, while TB infects 9.6 million people each year and kills 1.5 million, and malaria infects more than 200 million, killing nearly half a million. (Ali, smallpox’s last survivor, later succumbed to malaria.) Zika virus was first discovered in 1947 in Uganda in monkeys bitten by forest mosquitoes. In recent years, monkeys have sought food outside the forests, and Zika virus has diversified: its carriers now include Aedes aegypti, a tough mosquito with a preference for human blood and urban environments, and it has spread to the Americas. A. aegypti also carries dengue, yellow fever, and West Nile virus, but it is the evolving pan-epidemic of catastrophic birth defects that makes Zika particularly terrifying. In Brazil there have been 1,271 confirmed cases of microcephaly—babies born with severely stunted brains, blindness, and other congenital defects. Cases identified in Colombia, French Polynesia, Panama, Martinique, and Cabo Verde provide advance notice of the likely scale of the damage being wreaked. Zika provides a devastating backdrop for Sonia Shah’s Pandemic: Tracking Contagions from Cholera to Ebola and Beyond. But far from opportunism, the book represents six years’ work and considerable prescience on Shah’s part. A science writer and investigative journalist, she has a history of taking the long view. Her last book, The Fever, describes how malaria, an ancient parasite acquired from apes, has affected humans for half a million years, becoming a dominant influence on the success or failure of human efforts such as the colonization of North America. The success of the slave trade, for example, depended on the malaria resistance developed over centuries in Africa. As a doctor of pediatrics and public health, I have treated several hundred malaria patients on three continents during two decades, managed UNICEF’s malaria program in Somalia for the Global Fund to Fight AIDS, Tuberculosis and Malaria, and even contracted malaria myself. I wasn’t convinced I would learn much from Shah, nor did I have time for extraneous reading. Then last year, I found myself on Idjwi, a remote island in the Democratic Republic of Congo, treating scores of seriously ill children with malaria. Lacking electricity for lights, I read The Fever in the last hours of daylight after the clinic had closed. Shah’s synthesis of public health and politics, science and social behavior, provided new insight into malaria’s systematic contagion of mankind. When light faded each evening I dodged mosquitoes to take a brief bath in a lake infested with schistosomiasis, the second-most-common parasitic disease after malaria. Despite Brilliant’s position that pandemics are optional, the prevailing view in global health is that pandemics are inevitable. Shah’s thesis is that pandemics are the product of complex human behavior. In her view, development, urbanization, and population growth transform harmless animal microbes into human pathogens. Empire-building takes humans into animal habitats, while climate change caused by human activity and deforestation forces animals into urban areas; industrial poultry, cattle, and pig farms also bring humans into greater contact with animals. The “cholera paradigm” is a term coined by the microbiologist Rita Colwell. It means that the environment—biological, social, political, and economic—is both the source and driver of today’s emerging diseases in ways resembling the spread of cholera. Pandemics are caused by zoonoses—diseases that “jump” from animals to humans. Historically, this was a slow process, requiring considerable personal contact. Malaria took millennia to make the leap from primates to mankind. About ten thousand years ago, the dawn of agriculture and the domestication of livestock led to new levels of intimacy between humans and animals, which encouraged the emergence of our most familiar microbes. Cows gave us measles and TB; pigs gave us pertussis; ducks gave us influenza. Shah notes that, like us, microbes undergo natural selection for survival. Around the same time as the extinction of the smallpox virus, another virus was under threat. When the logging industry in Cameroon reduced the chimp population, simian immunodeficiency virus jumped from chimps to humans—a consequential choice since humans offered a host population of billions. When HIV appeared, rumors circulated of sexual congress between chimps and people as the means of transmission. In fact, we have our most intimate contact with animals when we consume them. On this point, Shah takes us to the wet markets of Guangzhou, China, where the SARS pandemic started in 2002. The markets flourished in the 1990s, as the rising incomes among China’s elite fed the demand for the wild game cuisine called yewei—including swans, peacocks, snakes, and turtles. Animals that would never be seen next to one another in the wild were forced into close proximity. Shah gets a good look at the scene in a market in Guangzhou—a turtle in a bucket next to wild ducks and ferrets, snakes close to civets. This unnatural confinement and proximity provides pathogens with the opportunities not only to mutate rapidly but also to jump species. The virus causing SARS spread from horseshoe bats to raccoon dogs, snakes, and civets, mutating along the way until it evolved sufficiently to infect humans. For centuries, cholera lived undisturbed in tiny crustaceans in the Bay of Bengal, until the arrival of the East India Company in the 1760s. Fishermen and rice farmers colonized five hundred square miles of wetlands, half-immersed in the natural habitat of the bacteria called Vibrio cholerae. Constant exposure to humans led to two important mutations: first, Vibrio grew a long tail that allowed it to, in Shah’s words, “stick to the lining of the human gut like scum on a shower curtain.” A second Vibrio mutation resulted in the toxin that causes massive diarrhea—and that makes cholera stool so infectious. In 1817, the first cholera pandemic started when Vibrio took advantage of the international traffic on the Spice Route. Since then, there have been seven separate cholera pandemics and hundreds of millions of deaths. Cholera spreads twice as fast as Ebola and kills considerably more quickly. People without detectable symptoms can carry the disease for several weeks, such as UN peacekeepers from Nepal who imported it into Haiti in 2010 with catastrophic and ongoing consequences. Today, cholera infects roughly three million people each year and kills almost 100,000. The seventh pandemic has been underway since 1961 and shows no signs of abating. In less than two hundred years, cholera has become the most successful and enduring of all pathogens. It is the ultimate traveler’s diarrhea. The cholera bacteria colonized Europe during the second pandemic of 1829–1851. Europeans called it “Asiatic cholera,” assuming Western civilization would be immune. Echoes of this complacency are seen in the modern response to Ebola, which was considered an African disease unworthy of investment until it arrived in Texas in September 2014.