Pandemic Influenza:
"Soldiers from Fort Riley, Kansas ill with Spanish influenza at a hospital ward at Camp Funston in 1918 where the worldwide pandemic began."
Three influenza pandemics (1918, 1957 and 1968) swept the globe in the 20th century and resulted in tens of millions of deaths, with each of these pandemics being caused by the appearance of a new strain of the virus in humans. The "Spanish" influenza pandemic of 1918–1919, which caused ≈50 million deaths worldwide, remains an ominous warning to public health.
As noted in the Journal of the American Medical Association final edition of 1918: "The 1918 has gone: a year momentous as the termination of the most cruel war in the annals of the human race; a year which marked, the end at least for a time, of man's destruction of man; unfortunately a year in which developed a most fatal infectious disease causing the death of hundreds of thousands of human beings. Medical science for four and one-half years devoted itself to putting men on the firing line and keeping them there. Now it must turn with its whole might to combating the greatest enemy of all-- infectious disease." (12/28/1918).
The emergence of an especially lethal avian H5N1 flu strain (bird flu) in Asia in the late 1990s, caused tremendous concerns about the possibility of another global pandemic. The highly pathogenic avian strain was responsible for widespread infection in poultry and waterfowl in Asia and sporadic outbreaks in other parts of the world. The spread of H5N1 virus from person-to-person has been limited and unsustained and the overall mortality in reported H5N1 cases is approximately 60%. Even if the highly pathogenic H5N1 avian virus did not lead to a pandemic, the human disease caused by it provided an example of a newly emerged influenza virus strain with a high mortality rate.
Recently, a new strain of influenza capable of causing severe disease and mortality in humans was identified in North America, leading to the declaration by the World Health Organization of the first pandemic of the 21st Century. The 2009 H1N1 virus (commonly refferd to as the "swine flu"), a triple reassortant virus with RNA genome segments from swine, avian and human viruses, was readily transmissible from human to human but caused a relatively milder disease with lower mortality rate than the H5N1 virus. CDC estimates that about 60 million Americans were infected with the 2009 H1N1 virus, 274,000 hospitalizations and 12,000 deaths occurred during the outbreak (http://www.cdc.gov/h1n1flu/estimates_2009_h1n1.htm).
The potential cost of a worldwide influenza pandemic is astounding. In 2008, the World Bank estimated that "A flu pandemic could kill 71 million people worldwide and push the global economy into a ``major global recession'' costing more than $3 trillion". The World Health Organization estimates that in a case of severe pandemic up to 25% of the world's population may be infected within a matter of months, and the death rate may reach 30% or higher.
"The pandemic clock is ticking; we just don't know what time it is."
Edgar Marcuse (former Chairman of the US National Vaccine Advisory Committee)