Thursday, June 12, 2014

Selected Readings on Human Health, Disease, and the Environment

The following are responses and summaries of various readings related to Human Health, Disease, and the Environment. 

Six Modern Plagues,  Chapter 5:  A Spring to Die For: Hantavirus
                Hantavirus pulmonary syndrome is a disease that has existed in the American Southwest since, at the very least, the time of Columbus’s exploration.  It invades the lungs of its victim and causes them to drown in their own fluid.  The disease is transmitted by the urine or saliva of mice.  When there is a great increase in the mouse population of the area there is a proportionate increase in the number of Hantavirus cases.  This was especially the case when in 1993 there was a great outbreak of the virus which has since been attributed to the recent heavy rains caused by El Nino.  Though the Navajo had knowledge of the disease for centuries before, what emerged for the rest of Americans was “a powerfully new, encompassing view of humans not as a stand-alone species but as just one species among many in a web of climate, ecology, and intertwined fates.”  The spring of 1993, just as the months before previous outbreaks, had seen a huge explosion of the mouse population in nearby rural areas.  The abundance of mice thereafter ventured into the cities and residential areas where the spread the disease to humans.

Chapter 6: A Virus from the Nile
                For the northern house mosquito, Culex pipiens, a native of the mid Northeastern Atlantic United States, a drought is heaven.  After feeding the female mosquito leaves her eggs in sewage, because sewage is teeming with nutrients.  Birds are mosquitos’ prey of choice, though they do occasionally feed on humans and other animals as well.  With each new victim the virus(es) contained within the mosquitoes’ bodies has a chance to move from the mosquito to a new host.  By a process known as amplification the virus can, using mosquitoes as vectors, spread rapidly and take root in millions of birds.  August and September of 1999 saw New York City receive its first cases of West Nile Virus, but months before the first human cases it was obvious that something was amok as hundreds of crows and other birds began turning up dead without apparent explanation.  Though many people believed that the drought had directly caused the deaths, it would not have done so in a controlled environment like the local zoo where captive birds fell prey. 
                The summer of 1998 was unusually hot in Israel, where thousands of white storks fly through during their migration from Europe to Africa every year.  This excess heat caused many of them to make more lengthy stays than usual in the eastern Mediterranean nation.  It is believed that these birds were the reason for the reintroduction of West Nile Virus back into the ecosystem there.  It is then believed that either an infected bird, mosquito, or human carried the virus to the United States and likely to Kennedy Airport near Queens, New York.  In only three years the virus had managed to make its way all across the continental U.S. to California, with hundreds of dead people and thousands of birds in its path.
Epilogue: SARS and Beyond
                According to the people who study epidemics it is only a matter of time until the next great pandemic.  Therefore it was not really surprising when SARS, the severe acute respiratory syndrome, took off so quickly in 2002.  It was the first disease to appear in the new century with epidemic possibilities.  Most recently HIV/AIDS, Ebola hemorrhagic fever, Lyme disease were the disease with outbreak potential.  SARS began in Guangdong Province, China in November 2002.  It causes headaches, muscle soreness, and dry coughs that quickly become pneumonia.  China managed to keep the outbreak under wraps until a man a doctor who had been in Guangdong traveled to Hong Kong where he caused the infection of many other people of different origination.  The virus then spread with its new hosts all throughout Southeast Asia but most surprisingly attached to a Canadian couple who then infected hundreds in the Toronto area; dozens died.  Today contagious disease is able to quickly spread across the globe due to the vast amount of daily international travel and the global black market.
                It is believed that SARS evolved from a disease which previously afflicted another species.  There are two ways a virus, or bacteria, may evolve.  It can merge with the genetic material of another organism or achieve a spontaneous genetic mutation.  Of the billions of possible random mutations very few are actually beneficial.  In the case of SARS, a mutation which was beneficial to the virus, i.e. allowing it to infect humans, was the result. 
Life Support, Chapter 6: Global Climate Change and Health
                The global temperature is constantly increasing.  It appears that there are more and more greenhouse gases in the atmosphere which are trapping additional amounts of heat within the surface of the Earth causing the planet to heat.  Mans combustion of fossil fuels, destruction of the world’s forests, irrigated agriculture, animal breeding, and manufacturing of cement seem to be the primary causes of these gases.  This all pinnacled in the 1990s, the hottest decade in the last 1000 years.  The global temperature is expected to rise 1.4 to 5.8 degrees C in the next 100 years.  Due to this violent and previously rare weather events like drought, floods, and storms are going to become more likely and occur much more often than before.  This can be seen with El Nino, which since the mid 70s has increased in frequency, magnitude and duration.
                The change in climate is the perfect breeding ground for the growth of previously controlled diseases. Cases of malaria and dengue fever are ever increasing in Africa, Asia, and Latin America.  Change in climate will increase vector-borne disease, intestinal infections, and death and injury caused by extreme weather events.   There will also be and increased rate of death from familiar causes as well as the emergence of new infectious diseases.  Studies have shown the viral maturation rates increase with an increase in temperature. 

 Readings above may have been drawn from the following sources:
Six Modern Plagues and How We are Causing Them, Mark Jerome Walters; Shearwater Books, 2003, ISBN 155963992X
Life Support, The Environment and Human Health, Michael McCally, editor, MIT Press, 2002, ISBN 0-262-63257-8
Rx for Survival,  Philip Hilts, Pengquin Books.  ISBN 0-7394-6974-6
Emerging Infectious Diseases,  Stuart A. Hill, Pearson Eductation Inc., publishing as Benjamin Cummings.  ISBN 0-8053-3955-8
Under the Weather:  Climate, Ecosystems and Infectious Disease, National Research Council, National Academy Press.  ISBN 0-309-07278-6

This article originally written September 16th, 2008 for OU IPE 3913 - Human Health, Disease, and the Environment.

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