A Messy Story - The Monster at Our Door: The Global Threat of Avian Flu - page 24

in Science provides an epistemological model for thinking about influenza emergence in south China and
elsewhere.
Explosive city growth in West Africa (where the urban population is expected to reach 60 million by
2025) drives an ever-growing demand for animal protein. Traditionally, West Africans, like many East
Asians, have consumed fish as their principal source of protein; fishing, moreover, is a major industry, em-
ploying nearly a quarter of the workforce in some countries. But local boats have been unable to compete
with the modern, government-subsidized fleets from Europe that now trawl the Gulf of Guinea. These
big factory fleets, along with foreign-flag pirate fishers, “illegally extract fish of the highest commercial
value, while . . . dumping 70 to 90 percent of their haul as by-catch.” As a result fish biomass has fallen
by at least half since 1977, and fish has become scarcer and more expensive in local markets. Increasingly
bushmeat (the generic name for the flesh of some 400 different species of terrestrial vertebrates) has been
substituted for fish—yearly some 400,000 tons of wild game now end up on West African dinner plates.
Like the practices that led to declining fish stocks, this level of hunting is unsustainable, and mammal
biomass is now decreasing at a rate that fundamentally threatens wildlife diversity. 91
The authors of this fascinating and troubling study, however, fail to connect a few all-important dots in
the causal chain, although undoubtedly they are aware of their importance. One is deforestation, as largely
foreign logging companies denude West Africa's remaining coastal rain forests. The bushmeat trade is
indissolubly linked to this logging juggernaut and the food needs of its workers, although hunters also
poach within official wildlife reserves as well, with the inevitable result being radically increased biolo-
gical contact between humans and wild animals. The formerly isolated microbiological reservoirs of the
rain forests and mountains have been inadvertently integrated into the food economy of the cities—and
the result of this “undercurrent of opportunity” has been a series of viral leaps from animals to humans.
The most infamous, of course, is HIV/AIDS: researchers believe that HIV-1 arose as a result of humans
eating chimpanzees, while HIV-2 (specific to West Africa) has been linked to the consumption of sooty
mangabeys. In the fall of 2004 a team headed by Nathan Wolfe of Johns Hopkins raised new fears with
the isolation of a novel HIV-like retrovirus (possibly from gorillas) in the bushmeat trade in Cameroon. 92
There is every reason to believe that the ecological impact of the recent urban-industrial revolution
in south China has been just as profound and far-reaching as urban population growth in West Africa.
Guangdong—long considered the epicenter of influenza evolution—has become the world's leading
export-manufacturing platform, a postmodern Manchester whose toys, running shoes, sports clothing, and
cheap electronics are consumed in every corner of the earth. From 1978 until 2002, the province's GDP
grew at an astonishing 13.4 percent per year, and the urban population of the Pearl River Delta area in-
creased from 32 percent to 70 percent of the total population. This spectacular regional transformation,
crowned by the return of Hong Kong to China in 1997, has been accompanied by a series of socioeco-
nomic developments that are also likely to reinforce Guangdong's primacy as a viral exporter.
Key parameters of influenza emergence include human and animal population densities, intensity of
contact between different species, and the prevalence of chronic respiratory or immune disorders. Popula-
tion densities are very high in the Delta, with about 1,273 persons per square kilometer. A large segment
of the population (indeed, the majority in the industrial boomtown of Shenzhen) are rural immigrants or
“floaters” in perpetual motion between city factories and thousands of rural villages. Without perman-
ent residency permits, these workers live in overcrowded dormitories or slums and are less likely than
the registered population to have access to modern medicine. Meanwhile, the state's share of healthcare
spending has fallen sharply (from 34 percent in 1978 to less than 20 percent in 2003) since the advent of
a market economy. “[A]bout 50 percent of people who are sick,” explains Yanzhong Huang, “do not see
a doctor because of the extremely high out-of-pocket payments.” 93 And rampant industrialization has in-
creased exposure to all sorts of environmental hazards and toxins. The Delta, for example, has monstrous