The widespread assumption that pandemic influenza is an exceptionally deadly form of seasonal, or nonpandemic, flu is hard to support, according to a new study in the May issue of the American Journal of Public Health.
The study challenges common beliefs about the flu--in particular the Centers for Disease Control and Prevention (CDC) claim that "the hallmark of pandemic influenza is excess mortality."
Peter Doshi, a graduate student in the History, Anthropology, and Science, Technology and Society Program at MIT, based his study on an analysis of more than a century of influenza mortality data. He found that the peak monthly death rates in the 1957-1958 and 1968-1969 pandemic seasons were no higher than--and were sometimes exceeded by--those for severe nonpandemic seasons.
Doshi says the pandemic-equals-extreme-mortality concept appears to be a generalization of a single data point: the 1918 season, a period in which "doctors lacked intensive care units, respirators, antiviral agents and antibiotics." He argues that "had no other aspect of modern medicine but antibiotics been available in 1918, there seems good reason to believe that the severity of this pandemic would have been far reduced."
As may be expected given improvements in living conditions, nutrition and other public health measures, influenza death rates substantially declined across the 20th century. Doshi calculates an 18-fold decrease in influenza deaths between the 1940s and 1990s, a trend that began far before the introduction of widespread vaccination.
Noting the gap between evidence and fear, Doshi identifies possible reasons that pandemic flu might be so misunderstood, including the possibility that commercial interests may be playing a role in inflating the perceived impact of pandemics. With public policies such as universal vaccination being discussed and more than $5 billion of federal money spent on preparing for the next pandemic, the study raises many important questions of public policy.
"Should the trends observed over the 20th century continue to hold in the 21st, the next influenza pandemic may be far from a catastrophic event," he concludes.
A version of this article appeared in MIT Tech Talk on April 16, 2008 (download PDF).
