Swine Flu in the Rearview Mirror

Epidemiology has long provided jobs for statistical analysis jocks, and right now the big question in epidemiology is swine flu.  How goes the war? 
 
The Centers for Disease Control began tracking the progress of the disease in April 2009, with the first laboratory-confirmed case of H1N1.  At the beginning of November a public health blogger responded to claims that predictions of a pandemic of Swine Flu had been exaggerated by pointing out that the CDC and the states stopped counting cases early in the pandemic and that even in the first wave of H1N1 there was significant underreporting.  
 
Citing an article that appeared in Emerging Infectious Diseases, the blog explains  a CDC/Harvard Medical School estimate of actual cases during the first four months of the pandemic (the explanation includes some very interesting detail on how epidemiologists try to get a grip on a very elusive population) .  The researchers used Monte Carlo software in a rearview mirror approach that combined risk analysis with a multiplier effect, a technique from statistical analysis, that adjusted the analysis at each step in the case identification process.
 

Using this technique the researchers estimated that for every laboratory-confirmed case of H1N1, there were actually 79 cases.  In other words, predictions of a pandemic were not hysteria.  And while public health officials are unlikely to get hard data that will allow them to measure the actual extent and severity of H1N1 infections, no doubt without efforts to prepare for the virus, their rearview mirror methods would eventually tell a much grimmer story.    

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