Viruses and Diseases, Emerging

In the global era, the easy mobility and transport of persons and material also allow for rapid global spread of disease-causing viruses. These result in pandemic outbreaks of global proportions.

One example of this is the 2009 influenza A (H1N1, also known as swine flu) outbreak. Preparations for it began long before, in 1997. In that year, it became apparent that an avian influenza virus designated H5N1 had jumped the species barrier from chickens straight to humans. For the preceding two decades, it had become apparent that influenza A was, at its heart, a truly avian virus and that the irregular global pandemics experienced in 1845, 1889, 1918, 1957, and 1968 could be explained by these avian influenza viruses jumping across from the bird reservoir. But until 1997, the domesticated pig remained at the center of the virology focus for a very important reason. As with bovine spongiform encephalopathy (BSE, also known as mad cow disease), humans are protected by our poorly understood yet powerful species barrier. A few viruses such as rabies can cross this barrier quite easily, from dogs and cats, and infect humans. Infrequently in history, diseases have crossed the barrier from chimpanzees to humans, as with HIV and hepatitis B. But overall, the barrier is rather firm and we remain safe from many zoonotic animal viruses and they, in turn, are safe from human viruses.

Influenza virologists had a working hypothesis involving the pig and this so-called species barrier. Theoretically, the barrier existed because of the inability of an avian influenza virus to actually latch onto cells in the human respiratory tree. As with orbiting spacecraft and their servicing rockets, at some stage, docking has to happen and the two crafts need to be a perfect fit. But docking of bird influenza virus on a human cell in the nose and throat just did not seem possible. The correct orientation of sugars was absent on the surface of the cells to allow virus docking. Then a group of scientists in Germany discovered that the cells of the domestic pig had both avian and human receptor sugars. So the farm pig could be a mixing vessel where avian influenza viruses could, albeit rarely, move across to mammals, perhaps swapping genes there with a human virus in the pig, and so emerge, now fully virulent, to the human world. Thus, the outbreak of H5N1 in Hong Kong in 1997 took virologists by surprise and moved the pig away from the center of the research focus. Public health officials moved into action. The events of 1997 catalyzed a huge international effort to actually prepare for a future influenza pandemic. In the past, scientists and public health professionals had just waited and handled the influenza attacks as best they could. Now a new spirit was abroad: Prepare a three-zone, in-depth defense system and [Page 1744]then venture out and destroy the vehicles of avian influenza, namely, the domestic birds. Antivirals and vaccines would be stockpiled as two defense zones and hygiene uplifted as the third. In short, the world had a war plan. Indeed, these battle plans began to be refined not only in governments but in businesses and homes. The European Union formulated a pandemic plan. These plans were spearheaded by World Health Organization (WHO) and the United Nations and were to prove critical in March 2009 and thereafter.

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