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Geography in the News: A Flu Diffusion Model

By Neal Lineback and Mandy Lineback Gritzner, Appalachian State University Pandemic Influenza Threats Influenza outbreaks cause real concern for world leaders who fear a global pandemic. The most recent flu virus is raging through 47 of the 50 U.S. states. Although it has peaked in a few states, it is important for the American public...

By Neal Lineback and Mandy Lineback Gritzner, Appalachian State University

Pandemic Influenza Threats

Influenza outbreaks cause real concern for world leaders who fear a global pandemic. The most recent flu virus is raging through 47 of the 50 U.S. states. Although it has peaked in a few states, it is important for the American public to understand the disease and how to prevent its spread, particularly among society’s most vulnerable.

Health officials have long predicted that a flu virus could evolve and could be deadly to millions of people worldwide. Although new strains of the influenza virus create some problems every year, until now none has been as virulent as the Spanish flu virus of 1918-19.

Most past influenza viruses originated in underdeveloped countries, some carrying geographic names from their suspected origins: Asian flu (1957), Hong Kong flu (1968), and Russian flu (1977). Although the deadly Spanish flu’s origin was actually somewhere in Asia, it created a pandemic of major proportions, killing 500,000 Americans and an estimated 20-50 million people worldwide.

Influenza viruses virtually always originate in either poultry or swine. The viruses may mutate and be transmitted to humans in close proximity to the infected animals. The viruses then may mutate further, creating person-to-person transmission routes. Once a contagious virus jumps to the human population and becomes capable of human to human infection, the “genie is out of the bottle,” so to speak, and it may begin its exponential spread around the world.

Recent scientific research has shown that the particularly deadly 1918-19 Spanish virus was a mutated avian (bird) virus, not unlike the 2005-06 H5N1 bird-flu virus. The 2005-06 strain apparently originated among poultry in the South China or Vietnam region. Despite predictions that the virus could have been the most serious flu ever with the potential for killing 180 to 360 million people (National Geographic), its effects were relatively mild.

Antibiotics have no effect on viruses. Preventive serums can help decrease individuals’ susceptibility to the flu. Because of the rapid mutation of flu viruses, however, the medical community must create a new serum each year to keep up with every new flu strain as the viruses mutate. Even then, there can be more than one virus in circulation, leaving inoculated people vulnerable. Nonetheless, the general consensus is that the flu vaccination provides considerable protection.

In today’s mobile world, the potential for a contagious disease being transported around the world is very real.  Mutated viruses circle the earth through our modern transportation systems, eventually reaching even the most isolated populations.

After jumping from animals to humans, influenza viruses may pass from person to person, depending on the proximity between the carrier and the receptor. Although there is debate about how long the viruses may remain active on environmental surfaces, such as doorknobs or toys, it is certain that they are easily transmitted between individuals through saliva, tears and other body fluids.

Geographic models can help explain likely avenues of influenza’s transmission and spread. Once the virus is introduced to a single individual in a population, new infections tend to radiate from that epicenter, somewhat like ripples on a pond. The virus may leapfrog to new centers, as infected individuals travel along transportation routes to other cities and towns. Rural residents with few contacts with major cities tend to avoid the virus until nearly the end of its geographic diffusion cycle.

The medical community now recognizes that any strategy to prevent or limit a virus’s spread must involve the social networks of babies, young children, adolescents, and adults. One of the first flu diffusion groups in any population is young children. As every parent knows, hygiene among groups of children is particularly difficult. Once a child in day care or elementary school is infected, other children and their families quickly fall victim as they handle each others’ toys, books and personal items.

Social contact at day care, school, work, shopping and recreation events and gatherings play prominent roles in the diffusion of flu viruses from person to person. Limiting such contacts—a strategy being currently used by individuals with weakened immune systems—can reduce the chance of infection, slow the diffusion rates and give health authorities time to implement other strategies.

Health officials warn that it is only a matter of time before this or another influenza virus evolves into deadly pandemic. Being prepared and taking precautions are the personal responsibilities of us all.

And that’s Geography in the NewsTM.

Sources: GITN 805, “Flu,” Oct. 2005; “Mexico struggles to contain swine flu,” (Associated Press), Winston-Salem Journal, Apr. 26, 2009; and Appenzeller, Tim. “Tracking the Next Killer Flu,” National Geographic, Oct. 2005.

Co-authors are Neal Lineback, Appalachian State University Professor Emeritus of Geography, and Geographer Mandy Lineback Gritzner. University News Director Jane Nicholson serves as technical editor.

This post is a revision of a Geography in the News article, GITN 987 Pandemic Influenza Threats, published in May 2009. Nearly 900 of the 1200, full-length weekly Geography in the News articles are available in the K-12 online education resource Maps101, including maps and other supporting materials and critical thinking questions.

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Meet the Author

Neal Lineback
Neal Lineback has written weekly Geography in the News (GITN) articles for more than 25 years (1,200 published articles) while he was Chair of Geography and Planning at Appalachian State University and since. In 2007, he brought his daughter Mandy Gritzner in as a co-author. She is also a geographer with a graduate degree from Montana State University. GITN has won national recognition and numerous awards from the Association of American Geographers, the National Council for Geographic Education and Travelocity, among others..