Current case counts for A/H3N2 variant is 289, with 15
hospitalizations and now finally we see our first fatality. The
hospitalization rate is 5.2%, which is more than 10 times the
hospitalization rate of pandemic H1N1. It is notable that we initially
projected a "ballpark" estimate of more than 15,000 cases before we would see our
first fatality, if the pediatric fatality rate was approximate to that
of pandemic H1N1 (i.e. 0.006%- see below). That is no longer the case. Obviously, observation of fatal cases can occur at any time within a sample size of 15,000.
CDC's estimates for cases, hospitalizations, and fatalities for the 2009 H1N1 pandemic are as follows:
Total cases (all ages): 61 milllion
Total hospitalizations (all ages): 274,000 (0.4%)
Total fatalities (all ages): 12,470 (0.02%)
Total pediatric cases: 20 million
Total pediatric hospitalizations (all ages): 87,000 (0.4%)
Total pediatric fatalities (all ages): 1,280 (0.006%)
Current CDC estimates for influenza A/H3N2 variant are as follows, which were posted 4 days ago:
289 cases since July 2012
15 hospitalizations (5.1%)
1 fatality (CFR 0.3%)
Therefore, current statistics place influenza A/H3N2 variant at more than 12x and a fatality rate 50x that of pandemic H1N1.
The question is, "how accurate are these stats?" We of course only know what we clinically recognize and test for. After years of monitoring influenza, one is reminded of the tremendous uncertainty associated with the ever-elusive denominator.
This has now become the "Super Bowl" of emergency public health. If HHS is able to recognize this agent going "hot" fast enough (i.e. recognition of sustained human-human transmission) to execute production of vaccine ahead of a wave of transmission, then public health will claim a major and significant victory. There is no guarantee this will happen, of course.
Influenza A/H3N2 variant is top infectious agent that should be on any operational biosurveillance analyst's radar.