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Chapter 17 : Plagues on Order
Many factors lead to the emergence of infectious diseases, some of which are obvious: a change in a parasite’s virulence, a breakdown in public health and surveillance measures, a change in human behavior, crowding, alterations in the environment, technological advances, economic downturns, poverty, and even something as innocent as foreign travel for a vacation. The disease is more prevalent in men than in women, probably as a result of the greater occupational exposure of men to rodents. Human-to-human transmission did not occur, but one wonders what would have been the result if the virus had acquired the capacity for pulmonary transmission, as happened with pneumonic plague. West Nile virus (WNV) was first isolated in 1937 from the blood of an infected woman in the West Nile country of Uganda. The woman had a rapid onset of fever, headache, backache, muscle pains, and anorexia. The most significant factor in all of the outbreaks was the involvement of the common house mosquito Culex pipiens as the vector. It is likely that WNV will advance through the United States within the next several years, and its path of death will be marked by the local and regional flyway patterns of virus-infected birds. Although sheep farmers tended to believe that scrapie was a hereditary disease, there was now mounting evidence that transmission was by sheep eating the afterbirth of an infected animal or grazing in a pasture where infected animals had been kept.