H5N1: Still Waiting in the Wings - An Updated Assessment of the Pandemic Flu Threat

Any highly transmissible disease has the potential to overwhelm local, regional, and perhaps even national medical and public health systems – while at the same time degrading critical- infrastructure/key-resource capabilities across all governmental and economic sectors. During a pandemic, the nation’s ability to respond to concurrent all-hazards emergencies at the federal, state, and local levels of government will also be severely diminished. Planning for a widespread infectious-disease outbreak is particularly important, because experts in this field agree that future pandemics are inevitable – but may be ameliorated to at least some extent. The timing and severity of those pandemics are the great unknowns. “Influenza pandemics can be expected to occur, on average, three to four times each century when new virus subtypes emerge and are readily transmitted from person to person,” according to a major 2004 report issued by the World Health Organization (WHO). However, the report continues, “the occurrence of influenza pandemics is unpredictable. In the 20th century, the great influenza pandemic of 1918–1919, which caused an estimated 40 to 50 million deaths worldwide, was followed by [other] pandemics in 1957–1958 and 1968–1969.” Avian influenza virus subtype H5N1 has emerged as a virus of particular concern in recent years because it “mutates rapidly and has a documented propensity to acquire genes from viruses infecting other animal species,” the WHO report also says. Moreover, although normally occurring in birds, some cases of human infection from H5N1 also have been documented. Ominous Statistics – Probably Underestimated The H5N1 infections, the Centers for Disease Control and Prevention (CDC) pointed out in a later (2007) report – Key Facts About Avian Influenza (Bird Flu) and Avian Influenza A (H5N1) Virus – “have generally resulted from people having direct or close contact with H5N1-infected poultry or contaminated surfaces.” In Thailand, the CDC noted, “probable human-to-human transmission was reported in 2004”; the likely cause was “prolonged and very close contact between an ill child and her mother.” Two years later (June 2006), the CDC also noted, “WHO reported evidence of human-to-human spread in Indonesia.”  Between 2003 and early September of this year, the World Health Organization said in a more recent report, there were 387 “confirmed cases of human avian influenza”; that number was based, though, on information received from only 15 countries. What was more alarming is that those 387 confirmed cases had caused 245 deaths – a fatality rate of 63.3 percent. It is likely a relatively large number of other cases had occurred during the same time frame but were not reported (the WHO figures were based solely on laboratory-confirmed cases). Because all influenza viruses have the ability to change, scientists are concerned that the H5N1 virus may eventually acquire the ability to infect humans directly, after which the virus could spread very quickly from one person to another – and, it seems very likely, from one country to another. Compounding this concern, the CDC pointed out in its 2007 report, is the fact that “there is little or no immune protection against these viruses in the human population.” Unlike seasonal influenza, the viruses that could cause a pandemic mutate from year to year. Another major factor that must be considered, commented Dr. Anthony Fauci of the National Institutes of Health (NIH), is that pandemic influenza is caused by a virus “that is dramatically different from those that have circulated previously.” Such viruses, Fauci said in a 2006 paper (Pandemic influenza threat and preparedness; Emerging Infectious Diseases), “can cause pandemics because few people, or none at all, have had prior immunologic exposure. “If the virus acquires the ability to transmit readily among humans,” he continued, “an influenza pandemic could ensue, with the potential to kill millions of people.” Fauci further noted that “the H5N1 avian influenza viruses now circulating [in 2006] may be the most likely candidates for triggering an influenza pandemic because of ongoing reports of new cases in humans.” Millions of Deaths, Trillions of Dollars The financial effects of such an outbreak would likely be staggering, and would probably affect all nations throughout the world. The World Bank said earlier this year that a severe influenza pandemic “could kill 71 million people and cause a recession costing more than $3 trillion.” Last year, Trust for America’s Health estimated that U.S. economic activity “would shrink 5.5 percent in a 1918-like pandemic, correlating to a 2005 Congressional Budget Office projection that a pandemic would cut the U.S. GDP [gross domestic product] by 5 percent.” The cost of a major pandemic would be not only financial, but political, social, and economic as well. High worker absenteeism, for example – and the resulting disruptions in the availability of critical-infrastructure and key-resource products and services – would significantly affect the national and global supply chains and therefore diminish the ability to respond to not only the pandemic event itself but also to other potentially catastrophic emergencies. In addition, an influenza pandemic that results in the closure of borders, causes high absenteeism, and disrupts the transport of commercial goods would significantly disrupt the availability of everyday essentials. Another factor to consider is that international travel is now such a routine aspect of everyday business and pleasure that it would allow individuals infected with highly contagious illnesses to travel to and from other countries within a matter of hours, all but guaranteeing the likelihood that infectious diseases would spread more rapidly today than was ever before possible. For that and many other reasons, the nation’s public-health community must continue to closely monitor the still evolving H5N1 situation – and at the same time be equally prepared to cope with any other contagion that could result in a highly transmissible infectious-disease outbreak. In short, even though the nation’s, and world’s, attention is now focused primarily on political and economic issues, Public Health must lead pandemic response-planning efforts in coordination and cooperation with all levels of government as well as with non-governmental organizations and the nation’s citizens at large.

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For Additional Information: On the 2007 CDC report, click on http://www.cdc.gov/flu/avian/gen-info/facts.htm

On Dr. Fauci’s paper, click on http://www.cdc.gov/ncidod/EID/vol12no01/05-0983.htm

On the World Bank’s estimated $3 trillion cost of a flu pandemic (developed by the University of Minnesota’s Center for Infectious Disease Research & Policy, Academic Health Center), click on http://www.cidrap.umn.edu/cidrap/content/influenza/biz-plan/news/oct1708economy.html

On the World Health Organization’s 2004 report on avian influenza and the significance of its transmission to humans, click on http://www.globalsecurity.org/security/library/report/2004/influenza_factsheet_who04.doc

On the 2008 WHO report on the Cumulative Number of Confirmed Human Cases of Avian Influenza A (H5N1), click on http://www.who.int/csr/disease/avian_influenza/country/cases_table_2008_09_10/en/index.html