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Bird Flu: A Virus of Our Own Hatching

In Bird Flu: A Virus of Our Own Hatching, Michael Greger, MD, depicts the human role in the evolution of the virus into a lethal mutant strain

Bird Flu: A Virus of Our Own Hatching

By Michael Greger, 416 pp, $30.
New York, NY, Lantern Books, 2006.
ISBN-13 978-1-5905-6089-1.

JAMA. 2007;298:1945-1946.

Worries about a forthcoming influenza pandemic have a solid historical foundation. Although the timing remains uncertain, flu pandemics have a relapsing pattern and incur enormous human and economic costs. Of the three 20th-century influenza pandemics, that of 1918-1919 is considered the most deadly disease event in human history.

The US Centers for Disease Control and Prevention (CDC) estimates that in a normal flu season some 200 000 individuals in the United States are hospitalized and 38 000 die of influenza, mostly elderly persons, with annual direct medical costs and lost productivity calculated at $12 billion. However, these figures pale before the catastrophe implied by a severe influenza pandemic. The CDC predicts that a medium-level epidemic would affect a third of the US population, hospitalize 734 000, and kill almost 210 000. With failure to produce an effective vaccine and with a virus untouched by anti-influenza drugs, an epidemic of the H5N1 avian influenza via person-to-person transmission could wreak havoc. With a probable 80 million disease episodes, a 20% mortality rate would result in 16 million deaths. The human tragedy and economic upheaval would be unprecedented.

The first cases of human infection by the highly contagious H5N1 avian influenza virus in Hong Kong in 1997 reinvigorated influenza research. This is an aggressive disease in fowl, with domestic chickens and turkeys being most severely affected (mortality exceeds 50%).

In Asia, the economic importance of poultry and poultry products has increased dramatically over the last 10 years, becoming a staple food that provides approximately 30% of total dietary protein, especially in rural households. Yet in several affected countries, up to 80% of poultry production occurs in backyard holdings and small rural farms.

Although outbreaks in poultry affect economies and food security, the greatest concern is that present conditions could trigger an influenza pandemic. However, the small number of human cases to date (approximately 150) suggests that H5N1 is not currently easily transmitted from birds to humans. Two mechanisms could change this. Effective interhuman transmission could follow the exchange of gene segments (ie, reassortment) when humans or pigs are simultaneously infected with H5N1 and a currently circulating human influenza virus is adapted for efficient transmission. The second mechanism is mutation during human infection, with only a small number of mutational changes thought to be needed.

What has happened for this innocuous intestinal bug, which has affected wild ducks for millions of years, to become a killer? In Bird Flu: A Virus of Our Own Hatching, Michael Greger, MD, depicts the human role in the evolution of the virus into a lethal mutant strain.

Greger, Director of Public Health and Animal Agriculture at the Humane Society of the United States, discusses how human mistreatment of animals has actually backfired, with factory farming making livestock more susceptible to disease. He explains how modern livestock production facilitates the transmission and evolution of avian influenza and argues convincingly that the right environment for a virus such as H5N1 to thrive now exists.

The message is that pandemics are not born but rather are man-made-and that there is a price to pay for the modern poultry industry, in which fowl are raised in closed, stressful, unhealthy facilities, facilitating mutation and dissemination of the bird flu virus. Greger writes that "[It] may take a pandemic with a virus like H5N1 before the world realizes the true cost of cheap chicken."

The Foreword is by Kennedy Shortridge, PhD, credited with discovering the H5N1 virus in Asia. The book subsequently contains 5 logically organized sections: an introduction to the history and biology of influenza ("Storm Gathering"), a discussion of the socioeconomic factors responsible for the increased threat of animal viruses to humans ("When Animal Viruses Attack"), an explanation of the antipandemic measures instigated in response to the emergence of H5N1 ("Pandemic Preparedness"), an overview of the individual measures available to combat a pandemic ("Surviving the Pandemic"), and a section entitled "Preventing Future Pandemics."

Greger also discusses other animal pathogens that may become human threats and argues that the environment that caused the emergence of the H5N1 virus can also trigger these transformations.

There remains room for hope. As Greger states in the Introduction, "[if] changes in human behaviour can cause new plagues, changes in human behaviour may prevent them in the future." A radical change from factory farming to less intensive methods including free-range farming is needed, especially in the poultry industry, in which "humanity must shift toward raising poultry in smaller flocks, under less stressful, less crowded and more hygienic conditions, with outdoor access."

Greger paints the science behind the bird flu virus, explaining recent theories on the evolution, pathogenesis, mutation, and spread of the virus. He discusses polemic issues such as the household storage of influenza antiviral agents and class differences in access to potentially scarce supplies of antivirals during a pandemic.

The book is timely, well-researched, and particularly incisive on farming methods worldwide, especially those for poultry. Although the repetition of the unavoidable horrors to come and our responsibility for them is sometimes wearying, this is a valuable resource for scientists and the public alike.

Financial Disclosures: None reported.

Xavier Bosch, MD, PhD, Reviewer
Department of Internal Medicine
University of Barcelona
Barcelona, Spain