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Epidemiology Essay

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Below is an essay on "Epidemiology" from Anti Essays, your source for research papers, essays, and term paper examples.

Influenza is spread from person to person by coughs and sneezes, but the virus doesn't begin its journey in a human host. Instead, wild aquatic birds such as ducks and shore birds perpetuate the influenza viruses that cause human pandemics. Although these birds carry the genes for influenza in their intestines, they usually don't become sick from the virus. And because they can migrate thousands of miles, the healthy birds can spread the virus across the globe even before the microbe makes contact with the human population.

As it happens, the form of the virus found in wild birds doesn't replicate well in human beings, and so it must first move to an intermediate host--usually domestic fowl or swine--that drinks water contaminated by the feces of aquatic birds. Horses, whales, seals and mink are also periodically infected with influenza. Although the intermediate hosts can sicken and die from the infection, swine can live long enough to serve as "mixing vessels" for the genes of avian, porcine and human forms of influenza. This occurs because swine have receptors for both avian viruses and human viruses.
Swine have probably played an important role in the history of the human disease. These animals appear to serve as living laboratories where the avian and mammalian influenza viruses can come together and share their genes (a reassortment of RNA segments) and create new strains of flu. When a strain of virus migrates into the human population, it changes into a disease-causing microbe that replicates in the respiratory tract. A sneeze or a cough spreads the virus in a contagious aerosol mist that is rich in virus particles. Most pandemics originate in China, where birds, pigs and people live in close proximity. Hong Kong's 1997 "bird flu" was an avian influenza virus that probably attained virulence through reassortment of genes from geese, quail and teal. Many bird species were housed together in the Hong Kong poultry markets, and this was an ideal...

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